:: What is Postfix
Postfix is a free and open-source mail transfer agent (MTA) that routes and delivers electronic mail. It is intended as a fast, easier-to-administer, and secure alternative to the widely-used Sendmail MTA. – WikiPedia
:: How to setup attachment size limit
+ checking limit size for attachment
postconf | grep message_size_limit # default is 10MB message_size_limit = 10240000
+ edit main.conf on this line
postconf -e "message_size_limit = 5240000"
+ checking new configuration
postconf | grep message_size_limit # change to 5MB message_size_limit = 5240000
+ restarting postif
/etc/init.d/postfix restart
