...making Linux just a little more fun!

<-- prev | next -->

Gmail on Home Linux Box using Postfix and Fetchmail

By Mike Chirico

Gmail on your Home Linux Box using Postfix and Fetchmail

Do you have a Gmail account? In that case, you'll want to read this step by step tutorial for configuring and installing the latest version of Postfix with SASL authentication and TLS encryption necessary for connecting and relaying Gmail to smtp.gmail.com. Plus, I'll walk you through configuring fetchmail (with STARTTLS), which will grab (fetch) Gmail to your local system. But it does not stop there. You'll learn how to forward mail to other computers you have in the house, plus how to automatically backup copies of email.

Quick Background

Postfix is a mail server, or MTA (Mail Transfer Agent). It accepts messages and delivers them. In contrast, fetchmail is a remote-mail retrieval system, providing home users like you (and me), who don't have corporate accounts, the ability to pull down mail from an ISP, or in this case Gmail, to our local Linux box. All examples are done and tested with the fake domain name "squeezel", which is my 4 year old's word for the concatenation of "squeeze" and "wheezel" (weasel). You should choose a unique, fake, domain name, or one that you do not anticipate going to on the Internet.

Safety First: Configure fetchmail with STARTTLS

It is very important to setup fetchmail with some type of encryption; otherwise, your Gmail password will be broadcast over the Internet every time the fetchmail daemon tries to pick up mail. In addition, this tutorial will walk you through building and configuring the latest version of Postfix with TLS and SASL support.

Getting Postfix Source: Latest Version, More Toys

1. Downloading Postfix Source

Get the latest version of Postfix. As of this writing, the latest version is 2.2.3, which was released on May 3, 2005. You can find out what version you have with the following command.

  $ postconf mail_version
   mail_version = 2.2.3

Download the latest version from the Postfix Home Page.

NcFTP is a popular alternative to ftp. If you don't have it, ftp or wget both work fine. This example is done with postfix-2.2.3 - Again, check for updates.

    $ ncftpget ftp://mirrors.loonybin.net/pub/postfix/official/postfix-2.2.3.tar.gz
    $ ncftpget ftp://mirrors.loonybin.net/pub/postfix/official/postfix-2.2.3.tar.gz.sig
    $ ncftpget ftp://mirrors.loonybin.net/pub/postfix/wietse.pgp

Next, import the PGP key.

    $ gpg --import wietse.pgp
    gpg: key C12BCD99: public key "Wietse Venema <wietse@porcupine.org>" imported
    gpg: key D5327CB9: public key "wietse venema <wietse@porcupine.org>" imported
    gpg: Total number processed: 2
    gpg:               imported: 2  (RSA: 2)

Verify that the source is valid:

    $ gpg --verify postfix-2.2.3.tar.gz.sig postfix-2.2.3.tar.gz

The next step is to unpack the file.

    $ tar -xzf postfix-2.2.3.tar.gz

2. Compiling Postfix with TLS and SASL support

Okay, you're connecting to Google's Gmail, so you'll need to compile Postfix with TLS (for encryption) and SASL (for authentication). You cannot send mail to your Gmail account without these.

2.1 First Upgrade OpenSSL and SASL

Special note: some older versions of Red Hat 8 and 9 may not have an updated version of openssl. Check to see what version you have with the following command:

    $ openssl version
    OpenSSL 0.9.7g 11 Apr 2005

If you need to upgrade openssl, find out where the current openssl directory is located. The default settings for openssl put it in /usr/local/ssl, but Red Hat and Fedora users have the following directory instead: /usr/share/ssl. Since my computers are Red Hat 9.0 and Fedora Core 2 and 3, the executable is /usr/bin/openssl and the related directories are /usr/share/ssl. Therefore, I'll compile it with the following settings:

    $ ./config --prefix=/usr  --openssldir=/usr/share/ssl
    $ make
    $ make test
    $ make install

2.2 Upgrading Cyrus SASL

You may have authentication problems without the latest upgrade. I had the following error in my /var/log/maillog with the default Fedora 3 install; however, the cyrus-sasl package from source fixed the problem.

    Authentication failed: cannot SASL authenticate to server smtp.gmail.com[]:
    no mechanism available

You can get the latest "cyrus-sasl" package from ftp://ftp.andrew.cmu.edu/pub/cyrus-mail/; make sure you search for the latest one. As of this writing, the latest version is 2.1.20.

    $  ncftpget ftp://ftp.andrew.cmu.edu/pub/cyrus-mail/cyrus-sasl-2.1.20.tar.gz

You will probably want to upgrade this package, as it provides new tools for creating certificates. Some older versions may cause problems when Postfix is compiled due to an outdated "ssh.h" file.

2.3 Add Postfix User (postfix) and Group (postdrop)

So, at this stage, you've upgraded openssl and sasl, correct? If you have authentication failures, then upgrade those packages. I had problems with Fedora Core 3 "rpm" installs, so I had to go back and upgrade.

Next, you will add "postfix" as a user. You don't want this user to have a home directory ("-M"), or login capability ("-s /sbin/nologin"). So, we create it like this:

    # useradd -M -s /sbin/nologin postfix
    # groupadd postdrop

2.4 Make Options

You do not need to add "postfix" to the group "postdrop" - it lives alone.

Now you are ready to run 'make'. If you need to re-run 'make', you should first issue the "make tidy" command to clean up the old files.

Choose "Option 1" below if you don't have MySQL. Postfix can work with MySQL tables, so it may be something you want to try later, after you get your Gmail working.

Cleaning Up Everything if Needed
    $ make tidy

Option 1: TLS and SASL2. You need at least these for Gmail.

    $ make makefiles CCARGS="-DUSE_TLS -DUSE_SASL_AUTH -I/usr/include/sasl" \
          AUXLIBS="-lssl -lcrypto -lsasl2"

Option 2: TLS, SASL2 and MySQL.

    $ make makefiles CCARGS="-DUSE_TLS -DUSE_SASL_AUTH -I/usr/include/sasl  -DHAS_MYSQL \
    -I/usr/local/include/mysql" AUXLIBS="-lssl -lcrypto -L/usr/local/lib/mysql -lmysqlclient \
    -lz -lm -lsasl2"
Or, if MySQL libs are in "/usr/lib/mysql", then, something like this:
    $ make makefiles CCARGS="-DUSE_TLS -DUSE_SASL_AUTH -I/usr/include/sasl  -DHAS_MYSQL \
    -I/usr/include/mysql" AUXLIBS="-lssl -lcrypto -L/usr/lib/mysql -lmysqlclient -lz -lm \
    $ make
    $ make install

2.5 Install Questions

After the "make install" you will be asked questions on where to place files. Unless you need to do otherwise, take the defaults. This will make it easy to follow the directions later.

There are questions prompted when running 'make install':

        Warning: if you use this script to install Postfix locally,
        this script will replace existing sendmail or Postfix programs.
        Make backups if you want to be able to recover.

        Before installing files, this script prompts you for some definitions.
        Most definitions will be remembered, so you have to specify them
        only once. All definitions should have a reasonable default value.

    Please specify the prefix for installed file names. Specify this ONLY
    if you are building ready-to-install packages for distribution to other
    install_root: [/]

    Please specify a directory for scratch files while installing Postfix. You
    must have write permission in this directory.
    tempdir: [/home/src/postfix/postfix-2.2.2]

    Please specify the final destination directory for installed Postfix
    configuration files.
    config_directory: [/etc/postfix]

 ... [SNIP] ...

    pages. You can no longer specify "no" here.
    manpage_directory: [/usr/local/man]

    Please specify the destination directory for the Postfix README
    files. Specify "no" if you do not want to install these files.
    readme_directory: [no]

2.6 What Libraries are Linked in?

Once you are done, as a check to see if ssl has been compiled into postfix, you can "ldd" the "postfix" file as follows, which will show the linked libraries.

    $ ldd /usr/sbin/postfix
        libssl.so.4 => /lib/libssl.so.4 (0x007ae000)
        libcrypto.so.4 => /lib/libcrypto.so.4 (0x006bb000)
        libmysqlclient.so.14 => /usr/lib/mysql/libmysqlclient.so.14 (0x00b28000)
        libz.so.1 => /usr/lib/libz.so.1 (0x00bf1000)
        libm.so.6 => /lib/tls/libm.so.6 (0x00afd000)
        libsasl2.so.2 => /usr/lib/libsasl2.so.2 (0x005f6000)
        libpcre.so.0 => /lib/libpcre.so.0 (0x00d46000)
        libdb-4.2.so => /lib/tls/i686/libdb-4.2.so (0x00201000)
        libnsl.so.1 => /lib/libnsl.so.1 (0x007e4000)
        libresolv.so.2 => /lib/libresolv.so.2 (0x00d30000)
        libc.so.6 => /lib/tls/libc.so.6 (0x009d1000)
        libgssapi_krb5.so.2 => /usr/lib/libgssapi_krb5.so.2 (0x006a5000)
        libkrb5.so.3 => /usr/lib/libkrb5.so.3 (0x0061b000)
        libcom_err.so.2 => /lib/libcom_err.so.2 (0x005f1000)
        libk5crypto.so.3 => /usr/lib/libk5crypto.so.3 (0x00682000)
        libdl.so.2 => /lib/libdl.so.2 (0x00b22000)
        libcrypt.so.1 => /lib/libcrypt.so.1 (0x032cb000)
        /lib/ld-linux.so.2 (0x009b7000)
        libpthread.so.0 => /lib/tls/libpthread.so.0 (0x00c13000)

Looks like they're all installed. Above the first line with "libssl.so" shows that I have "ssl" installed; then, 6 lines down after the command you will see "libsasl2.so.2". So, in my version, did I choose MySQL? The best way to tell is with the "postconf -m" option. But, yes, some of you may have a sharp eye and noticed the "libz" and "libm" linked in, which goes with the MySQL install.

2.7 Accessible Shared Libraries

By the way, if you get odd MySQL errors during the "make install", and your mysql libraries live in "/usr/local/lib/mysql", then you may need to add an entry in your "/etc/ld.so.conf" file to include "/usr/local/lib/mysql" as follows:

     $ cat /etc/ld.so.conf

After adding this line, you must run the "ldconfig" command. Now, all those odd mysql libraries will be found. It's good technique if you install a lot of software from source.

At this stage, there are still some postfix configuration settings. You'll get back to them; but first, it makes sense to generate the "Certificates".

3. Generating Certificates

Again, before getting started, make sure you have the latest version of openssl. As of this writing, 0.9.7g is the latest version. See the steps above if you decide to upgrade.

    $ openssl version
    OpenSSL 0.9.7g 11 Apr 2005

3.1 Creating Your Own Certificate Authority (CA)

You can get signed certificates from Thawte and VeriSign; but you don't have to for your home system. Instead, you will become your own "Certificate Authority", and sign your own SSL certificates.

This is the command to create your own CA. Hit 'return' for the first prompt to create the CA. It will prompt you for a password, and prompt to confirm. Remember the password. Also, it's important that the "Organization Name" match, when you create the "server" certificate. Below I have shown you my answers in bold, so you can see how they will match when creating and signing certificates.

    $ /usr/local/ssl/misc/CA.pl -newca
      CA certificate filename (or enter to create)

      Making CA certificate ...
      Generating a 1024 bit RSA private key
      writing new private key to './demoCA/private/cakey.pem'
      Enter PEM pass phrase: password123
      Verifying - Enter PEM pass phrase: password123
      You are about to be asked to enter information that will be incorporated
      into your certificate request.
      What you are about to enter is what is called a Distinguished Name or a DN.
      There are quite a few fields but you can leave some blank
      For some fields there will be a default value,
      If you enter '.', the field will be left blank.
      Country Name (2 letter code) [US]:US
      State or Province Name (full name) [Pennsylvania]:Pennsylvania
      Locality Name (eg, city) []:Elkins Park
      Organization Name (eg, company) []:Chirico_Widgets


By the way, if after doing the above command you find that you want to extend the key - say you didn't change the "default_days = 3650", or you did and want to change it back, then, you can issue the following command.

  Manual method to go back and change days value

    $ openssl x509 -in demoCA/cacert.pem -days 1024 -out cacert.pem -signkey \
    $ cp cacert.pem demoCA

Or, you could hard-code these values in "/usr/openssl.cnf", if you find that you're doing this over and over for testing. However, as you can see from the above command, it is easy enough to change the values.

3.2 Generate the Server Certificate

This is the server certificate request that will be signed by the CA Authority.

Note, below that the "-nodes" option is used so that the certificate will not require a pass phrase each time the secure daemon is started. Below I have also added my fake domain name "squeezel.squeezel.com", and

    $ openssl req -new -nodes \
      -subj '/CN=squeezel.squeezel.com/O=Chirico_Widgets/C=US/ST=Pennsylvania/L=Elkins Park' \
       -keyout FOO-key.pem -out FOO-req.pem -days 3650

Note above that "/0=Chirico_Widgets" must match the name given in the the original CA. For example, "/0=Widgets co." will not work, because it doesn't match. It must be exact.

3.3 Sign the Server Certificate

The following steps will sign the certificate.

    $ openssl ca -out FOO-cert.pem -infiles FOO-req.pem

3.4 Copy Signed Certificates to /etc/postfix/certs

The next step copies over all the required certificates to where Postfix can find them. In addition, the correct rights are enforced on each file.

   $ cp demoCA/cacert.pem FOO-key.pem FOO-cert.pem /etc/postfix
   $ chmod 644 /etc/postfix/FOO-cert.pem /etc/postfix/cacert.pem
   $ chmod 400 /etc/postfix/FOO-key.pem

4. Configuring Postfix

The file "/etc/postfix/main.cf" and "/etc/postfix/master.cf" are the two basic Postfix configuration files.

Postfix is particular about the hostname of your computer. You can have a fake hostname. In fact, the fake hostname that I am using is "squeezel.squeezel.com". Pick a name and set it up as follows. By the way you can actually use "squeezel.squeezel.com" if you want, since it's not a real domain name; but, you might want to use something more descriptive. The point here is it doesn't have to be registered to you; but it does have to be unique.

4.1 Configure the Hostname

The computer that these examples are taken from is "squeezel.squeezel.com", and it exists on IP address The short name is just "squeezel". Another computer, on IP address "" is "tape.squeezel.com".


    # Do not remove the following line, or various programs
    # that require network functionality will fail.       localhost.localdomain           localhost    squeezel.squeezel.com           squeezel   tape.squeezel.com               tape

You may also want to edit "/etc/sysconfig/network" and add or check the following.


Finally, to put all changes into effect now, run the following command with root privileges.

   $ hostname squeezel.squeezel.com

Some of the settings in the postfix main.cf file depend upon the hostname.

4.2 main.cf

The following settings can be added to the end of the "/set/postfix/main.cf" file. Postfix reads this file from top to bottom, taking the last values assigned in this file.

    ##   Add these lines to the bottom on main.cf

    ## TLS Settings
    smtp_tls_CAfile = /etc/postfix/cacert.pem
    smtp_tls_cert_file = /etc/postfix/FOO-cert.pem
    smtp_tls_key_file = /etc/postfix/FOO-key.pem
    smtp_tls_session_cache_database = btree:/var/run/smtp_tls_session_cache
    smtp_use_tls = yes
    smtpd_tls_CAfile = /etc/postfix/cacert.pem
    smtpd_tls_cert_file = /etc/postfix/FOO-cert.pem
    smtpd_tls_key_file = /etc/postfix/FOO-key.pem
    smtpd_tls_received_header = yes
    smtpd_tls_session_cache_database = btree:/var/run/smtpd_tls_session_cache
    smtpd_use_tls = yes
    tls_random_source = dev:/dev/urandom

    ##  SASL Settings
    # This is going in to THIS server
    smtpd_sasl_auth_enable = no
    # We need this
    smtp_sasl_auth_enable = yes
    smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
    smtpd_sasl_local_domain = $myhostname
    smtp_sasl_security_options = noanonymous
    #smtp_sasl_security_options =
    smtp_sasl_tls_security_options = noanonymous
    smtpd_sasl_application_name = smtpd

    ## Gmail Relay
    relayhost = [smtp.gmail.com]

    ## Good for Testing
    # sender_bcc_maps = hash:/etc/postfix/bcc_table

    # Disable DNS Lookups
    disable_dns_lookups = yes
    # Great New feature Address Mapping
    #  for example may mchirico@localhost to mchirico@gmail.com
    smtp_generic_maps = hash:/etc/postfix/generic
    transport_maps = hash:/etc/postfix/transport

The TLS settings are pretty standard, and the above code is taken from the documentation, which is worth a read. Note the "*.pem" files would appear to be listed twice; however, notice the difference between "smtp" and "smtpd". One is for client connectivity and the other is for connecting to this server.

4.3 sasl_passwd

In the above "main.cf" file, there are several hashed files, or Berkeley DB files which will have to be created. Look again at the recommended entries in "main.cf", and you will notice "hash:" in front of these values. For example "hash:/etc/postfix/sasl_passwd".

Below is a sample sasl_passwd file. This will login to smtp.gmail.com with username mchirico, using the password pa33w0r8.

    # Contents of sasl_passwd
    [smtp.gmail.com]              mchirico@gmail.com:pa33w0r8

Next, this file must be converted to hash format, with the following command.

    $ cd /etc/postmap
    $ postmap sasl_passwd

The "postmap" command must be run anytime "sasl_passwd" is changed, because this creates the "sasl_passwd.db" that postfix reads.

After you have run the above command, run this simple "hash" key test.

    $ postmap -q [smtp.gmail.com] sasl_passwd

4.4 generic

The file "/etc/postfix/generic" contains the following entries.

    chirico@squeezel.squeezel.com         mchirico@gmail.com

4.5 transport

    # Contents of /etc/postfix/transport
    # This sends mail to Gmail
    gmail.com               smtp:[smtp.gmail.com]
    # Except mail going to the tape and closet server
    tape.squeezel.com        relay:[tape.squeezel.com]
    closet.squeezel.com      relay:[closet.squeezel.com]

The transport file sends all email to Gmail or "smtp.gmail.com", but internal mail on my network is relayed to the appropriate servers. From above, sending an email to "root@tape" does not route it to the google account. The return address is "chirico@squeezel.squeezel.com" because of the following entry in "master.cf".

4.6 master.cf

This file must be owned by root. Whenever changes are made to this file, postfix should be reloaded with "postfix reload" command.

   smtp      unix  -       -       n       -       -       smtp
   relay     unix  -       -       n       -       -       smtp
        -o smtp_generic_maps=

Note the empty "smtp_generic_maps=" with nothing after the equals sign. This means anything relayed, anything going to "tape.squeezel.com" or "closet.squeezel.com" will not have an address translation - only the email going out to Gmail. What about mail from "squeezel.squeezel.com" to itself? No address translation either, which is a feature of "smtp_generic_maps".

That is it for the server certificate. Postfix will still have to be configured to connect to your ISP.

4.7 Postfix setup - utilizing "postconf -n"

To see if all the changes went into effect, here is the output of the "postconf -n" command.

    [root@squeezel ~]# postconf -n
    command_directory = /usr/sbin
    config_directory = /etc/postfix
    daemon_directory = /usr/libexec/postfix
    debug_peer_level = 2
    disable_dns_lookups = yes
    html_directory = no
    mail_owner = postfix
    mailq_path = /usr/bin/mailq
    manpage_directory = /usr/local/man
    newaliases_path = /usr/bin/newaliases
    queue_directory = /var/spool/postfix
    readme_directory = no
    relayhost = [smtp.gmail.com]
    sample_directory = /etc/postfix
    sendmail_path = /usr/sbin/sendmail
    setgid_group = postdrop
    smtp_generic_maps = hash:/etc/postfix/generic
    smtp_sasl_auth_enable = yes
    smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
    smtp_sasl_security_options = noanonymous
    smtp_sasl_tls_security_options = noanonymous
    smtp_tls_CAfile = /etc/postfix/cacert.pem
    smtp_tls_cert_file = /etc/postfix/FOO-cert.pem
    smtp_tls_key_file = /etc/postfix/FOO-key.pem
    smtp_tls_session_cache_database = btree:/var/run/smtp_tls_session_cache
    smtp_use_tls = yes
    smtpd_sasl_application_name = smtpd
    smtpd_sasl_auth_enable = no
    smtpd_sasl_local_domain = $myhostname
    smtpd_tls_CAfile = /etc/postfix/cacert.pem
    smtpd_tls_cert_file = /etc/postfix/FOO-cert.pem
    smtpd_tls_key_file = /etc/postfix/FOO-key.pem
    smtpd_tls_received_header = yes
    smtpd_tls_session_cache_database = btree:/var/run/smtpd_tls_session_cache
    smtpd_use_tls = yes
    tls_random_source = dev:/dev/urandom
    transport_maps = hash:/etc/postfix/transport
    unknown_local_recipient_reject_code = 550

4.8 Common Postfix Commands

    $ /etc/init.d/postfix restart   # restarts postfix needed for inet_interfaces changes
    $ postfix reload                # reloads most changes in main.cf
    $ postfix check                 # checks postfix configuration
    $ postconf -n                   # dumps setting that went into effect
    $ postconf -m                   # shows the map types: mysql, hash, regexp ...
    $ postmap <filename>            # creates a map file for transports, sender_canonical etc.
    $ postqueue -p                  # checks the queue
    $ postsuper -d ALL              # deletes all messages in the queue
    $ postsuper -d AC8231EDA2D      # deletes message AC8231EDA2D
    $ postconf mail_version         # this tells you what version of Postfix you are using

4.9 MySQL

Instead of using the hash type, you can leverage MySQL. Below is a sample "smtp_generic_maps" configuration for converting addresses. The text below is the "/etc/postfix/generic_mysql" file. Note, that is contains the MySQL username, password for MySQL, and the database "dbname" in this file. The comments show how this table was created in MySQL.

    #  The entry in main.cf is
    #    smtp_generic_maps = mysql:/etc/postfix/generic_mysql
    # This is the MySQL table definition
    # create table smtpg_maps (
    #  pkey int NOT NULL auto_increment,
    #  address varchar(50),
    #  smtp_address varchar(50),
    #  timeEnter timestamp(14),
    #  PRIMARY KEY (pkey));
    #  insert into smtpg_maps (address,smtp_address) values ('chirico@squeezel.squeezel.com',
    #  'mchirico@gmail.com');
    #  insert into smtpg_maps (address,smtp_address) values ('lpayne@squeezel.squeezel.com',
    #  'payne.lisa@gmail.com');
    #  insert into smtpg_maps (address,smtp_address) values ('root@squeezel.squeezel.com',
    #  'mike.chirico@gmail.com');
    # Test this with
    #  $ postmap -q "root@squeezel.squeezel.com" mysql:/etc/postfix/generic_mysql
    hosts = localhost
    user = mysqlmail
    password = S0m3paSSw0r9
    dbname = mail
    query = SELECT smtp_address  FROM smtpg_maps WHERE address = '%s'

4.10 Additional Items

If you are using Fedora Core, which defaults to Sendmail, you may need to make a few configuration changes. For example, you may be picking up the incorrect version of sendmail.

     $  alternatives --config mta

      There are 2 programs which provide 'mta'.

      Selection    Command
      *+ 1           /usr/sbin/sendmail.sendmail
      2           /usr/sbin/sendmail.postfix

      Enter to keep the current selection[+], or type selection number:

You will want to select 2, above. If you now do an "ls" on 'sendmail', you will see the following results:

$ ls -l /usr/sbin/sendmail
  lrwxrwxrwx  1 root root 21 Jan 13 20:53 /usr/sbin/sendmail -> /etc/alternatives/mta
  [root@squeezel ~]# ls -l /etc/alternatives/mta
  lrwxrwxrwx  1 root root 26 Apr 28 10:23 /etc/alternatives/mta -> /usr/sbin/sendmail.postfix

Now try sending email. The "correct" sendmail will build a report that you can view with "mutt" or any other email client. Below is an example of a test:

    $ sendmail -bv zmchirico@yahoo.com

4.10.1 Backups with bcc

Any mail sent out from "gmchirico@squeezel.squeezel.com" can be blind copied to another server. In this case the server is "chirico@tape".

    Contents in /etc/postfix/main.cf
      sender_bcc_maps = hash:/etc/postfix/bcc_table

Remember to "postmap bcc_table" after editing the bcc_table file.

    Contents of  /etc/postfix/bcc_table
     gmchirico@squeezel.squeezel.com chirico@tape

If you want to get copies of everything coming in and going out, then use the "always_bcc" option. I normally create a special user for this "allmail", that way I can forward email easily if needed.

    Setting in /etc/postfix/main.cf
     always_bcc = allmail

It's not a completely blind copy, since it will show up when users on the system do a "sendmail -bv" test.


Why Fetchmail?

Fetchmail pulls the email down from Google's Gmail, since for a home user with a fake domain and changing IP address, their email server will not forward the email.

5. Safety First: Configure fetchmail with STARTTLS

Again, it is very important to setup fetchmail with some type of encryption. STARTTLS encryption works well, since you have already installed the necessary openssl files. You just need to pick up the necessary keys and put them in the proper format.

5.1 Google Gmail Certificates

    $ openssl s_client -connect smtp.gmail.com:995 -showcerts

The command above will return the certificate from Google's Gmail as follows:

CONNECTED(00000003) --- Certificate chain
 0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=pop.gmail.com
   i:/C=ZA/ST=Western Cape/L=Cape Town/O=Thawte Consulting cc/OU=Certification Services
   Division/CN=Thawte Server CA/emailAddress=server-certs@thawte.com
Server certificate
subject=/C=US/ST=California/L=Mountain View/O=Google
Inc/CN=pop.gmail.com issuer=/C=ZA/ST=Western
Cape/L=Cape Town/O=Thawte Consulting
cc/OU=Certification Services Division/CN=Thawte Server
No client certificate CA names sent
SSL handshake has read 994 bytes and written 338 bytes
New, TLSv1/SSLv3, Cipher is DES-CBC3-SHA
Server public key is 1024 bit
    Protocol  : TLSv1
    Cipher    : DES-CBC3-SHA
    Session-ID: A3A9A02C84C4493291374B3B749819F4A801ECBCA1024EAA54E40534EEE4D60F
    Master-Key: D7C08FBB9A69143EBA8AFAB9F920979C4A27415B514ADF3ABF13FD8D0A8335F8
    Key-Arg   : None
    Start Time: 1115220880
    Timeout   : 300 (sec)
    Verify return code: 21 (unable to verify the first certificate)
+OK Gpop ready.

5.2 Extract Certificate

Next, you need to copy the certificate part, which is everything between the "BEGIN CERTIFICATE" part and "END CERTIFICATE" part, and save this to a file.


However, notice above that the CA for this certificate is thawte.com, which means you need that certificate as well. This is a very common certificate. Normally you can cut and paste them from "/usr/share/ssl/cert.pem".

If you look closely at that file you'll see the certificate. Or, you can copy it from below.

5.3 Certificate of the CA - Thawte

Thawte Server CA
MD5 Fingerprint: C5:70:C4:A2:ED:53:78:0C:C8:10:53:81:64:CB:D0:1D
PEM Data:

To recap: you should have the two certificates saved to separate files. In my case I've labeled them googlepop.pem and thawte.pem

5.4 Rehash or Creating Symlinks

Once you have created these files, you will need to run the "c_rehash" command to create the necessary sym-links. I've copied the files in "/home/chirico/certs/.certs". Then, shown below the running the "c_rehash" command.

    [chirico@squeezel certs]$ c_rehash .certs
    Doing .certs
    googlepop.pem => 34ceaf75.0
    thawte.pem => ddc328ff.0

5.5 Checking the Certificate

It's possible to check the certificates as with the "openssl s_client" command as follows:

    $  openssl s_client -connect pop.gmail.com:995 -CApath /home/chirico/certs/.certs/
    depth=1 /C=ZA/ST=Western Cape/L=Cape Town/O=Thawte Consulting cc/OU=Certification Services
    Division/CN=Thawte Server CA/emailAddress=server-certs@thawte.com
    verify return:1
    depth=0 /C=US/ST=California/L=Mountain View/O=Google Inc/CN=pop.gmail.com
    verify return:1
    Certificate chain
     0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=pop.gmail.com
       i:/C=ZA/ST=Western Cape/L=Cape Town/O=Thawte Consulting cc/OU=Certification Services 
       Division/CN=Thawte Server CA/emailAddress=server-certs@thawte.com
    Server certificate
    ... [SNIP] ...
    +OK Gpop ready.

5.6 The Fetchmail config .fetchmailrc

Note that the fetchmail option sslcertck, seen below in the ".fetchmailrc" file, causes fetchmail to strictly check the server certificate against a set of local trusted certificates.

Below is a sample ".fetchmailrc" file, the file that should be stored in your home directory.

    # Sample /home/chirico/.fetchmailrc file for Gmail
    # Check mail every 90 seconds
    set daemon 90
    set syslog
    set postmaster chirico
    #set bouncemail
    # Google Gmail  is mchirico but on computer it is chirico
    #  To keep mail on the server use the you would put keep at the end.
    # user 'mchirico@gmail.com' with pass "pa33w0r8"  is 'chirico' here options ssl sslcertck
    # sslcertpath '/home/chirico/certs/.certs' keep
    poll pop.gmail.com with proto POP3 and options no dns
	 user 'mchirico@gmail.com' with pass "pa33w0r8"  is 'chirico' here options ssl
	 sslcertck  sslcertpath '/home/chirico/certs/.certs'
         smtphost localhost
    # You would use this to by-pass Postfix
    # mda '/usr/bin/procmail -d %T'

Normally you would want to start fetchmail with the "-v" option and take a look at the "/var/log/maillog" files for any problems.

5.7 Fetchmail Commands

Below are some of the more common fetchmail commands.

    $ fetchmail -q    # quits fetchmail daemon
    $ fetchmail -v    # start fetchmail daemon in verbose mode
    $ fetchmail -c    # checks for email only
    $ fetchmail -S localhost # delivers mail to you Postfix server

Recommended Reading


(For more tutorials by this author, please see his Soup to Nuts site.)


[BIO] Mike Chirico, a father of triplets (all girls) lives outside of Philadelphia, PA, USA. He has worked with Linux since 1996, has a Masters in Computer Science and Mathematics from Villanova University, and has worked in computer-related jobs from Wall Street to the University of Pennsylvania. His hero is Paul Erdos, a brilliant number theorist who was known for his open collaboration with others.
Mike's notes page is souptonuts.

Copyright © 2005, Mike Chirico. Released under the Open Publication license unless otherwise noted in the body of the article. Linux Gazette is not produced, sponsored, or endorsed by its prior host, SSC, Inc.

Published in Issue 115 of Linux Gazette, June 2005

<-- prev | next -->