mime_log : file
MIME message-related alerts are logged to this file.
mime_sessions : table[conn_id] of mime_session_info
A table, indexed by connection ID, of mime_session_info
records, characterizing each MIME session.
check_relay_3 function(session: mime_session_info, msg_id: string): bool
Fixme: Don't know about this
check_relay_4 function(session: mime_session_info, content_hash: string): bool
Fixme: Don't know about this