bsd.b3ta.org
Yet another *nix admin blog

I’ve been experimenting with numerous postfix features since Kaeru introduced me to this beast last year. One of them is Address verification. It is a feature that allows the Postfix SMTP server to block a sender (MAIL FROM) or recipient (RCPT TO) address until the address has been verified to be deliverable. The idea is to reject junk mail with an unreplyable sender address.

However, this feature is available in Postfix version 2.1 and later. The implementation is simple and clearcut.

CONFIGURATION

The following configuration is an example for Sender address verification for mail from frequently forged domains where selective domains were picked for address verification.

/usr/local/etc/postfix/main.cf

smtpd_sender_restrictions = permit_mynetworks,
    check_sender_access hash:/usr/local/etc/postfix/sender_access

/usr/local/etc/postfix/send_access:-

hotmail.com    reject_unverified_sender

Note : remember to hash the sender_access file with postmap and reload your postfix.

SENDER ADDRESS VERFICATION IN ACTION

In this example, verification email was generated (from : postmaster@mymx.com) and used to verify the existence of user@hotmail.com.

May 21 12:06:44 mail postfix/cleanup[82710]: 7DE43EBE8A: Message-id=<20070521040644.7DE43EBE8A@mail.mymx.com>
May 21 12:06:44 mail postfix/qmgr[82697]: 7DE43EBE8A: from=
, size=271, nrcpt=1 (queue active)
May 21 12:06:45 mail postfix/smtp[82704]: 7DE43EBE8A: to=, relay=mx2.hotmail.com[65.54.245.40]:25, delay=0.81, delays=0/0/0.61/0.2, dsn=2.0.0, status=deliverable (250 user@hotmail.com )
May 21 12:06:45 mail postfix/qmgr[82697]: 7DE43EBE8A: removed

OBSERVATIONS

Sender address verification is useful. However, excessive verification attempts may keep your box busy or under heavy load. Just imagine your daily email volume is 100K emails. With sender address verification, your box needs to verify all of them before receiving them. This is merely my personal observation. Your mileage may vary.

REFERENCE

http://www.postfix.org/ADDRESS_VERIFICATION_README.html

Thoughts Aside
The concept behind any internet marketing program should be clearly outlined before it is implemented. That means that whether you are going to adopt email marketing or any other form of web marketing, the basic plan should be crystal clear in your mind. This in turn leads to effective internet marketing. This is the way search engine optimization is done.

This entry was posted on Monday, May 21st, 2007 at 12:44 pm and is filed under Howto, Misc. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.