King0770-Notes-Header-Checks

Revision as of 17:54, 19 October 2011 by King0770 (talk | contribs) (Section IV - Header checks syntax by example)

Section I - General Info

As a long time fan of Postfix, I use Postfix's header_check feature to discard messages I don't want coming off the wire. In my opinion, using Postfix to discard unwanted messages is a good way to keep spam messages away. However, using header_checks must be used with care. The purpose of this wiki is to guide you to add your own header_checks file for the Zimbra-MTA system.

Section II - Prepare ZCS Machines

First, look at the postfix_header_checks in Zimbra's localconfig.

zmlocalconfig | grep header_checks

Most likely you will see the following:
postfix_header_checks = pcre:/opt/zimbra/conf/postfix_header_checks

Now, lets create our own header_checks file. Note: For this wiki, I am going to create a "custom_header_checks" file, but you can create your own file.

touch /opt/zimbra/conf/custom_header_checks

zmlocalconfig -e postfix_header_checks="pcre:/opt/zimbra/conf/postfix_header_checks, pcre:/opt/zimbra/conf/custom_header_checks"

zmmtactl restart

zmlocalconfig | grep postfix_header_checks

You should see:
postfix_header_checks = pcre:/opt/zimbra/conf/postfix_header_checks, pcre:/opt/zimbra/conf/custom_header_checks

Don't forget to use postconf to make sure the changes are picked up.

postconf | grep header_checks

Section III - Editing your custom header checks file

Editing your /opt/zimbra/conf/custom_header_checks is fairly straight forward, just use your favorite editor, i.e vi, nano, emacs.

No need to run postmap against the /opt/zimbra/conf/custom_header_checks

Section IV - Header checks syntax by example

In the interest of brevity and simplicity, I am only going provide a few examples. Honestly, I've only scratched the surface of this feature.

/^Subject:(.*)From U.S. Ambassador to Nigeria/   DISCARD #spam rule no msgs from Nigeria

/^Subject:(.*)\?KOI8-R\?/ DISCARD #spam rule Russian encoding not allowed by this server

/^From:(.*)Slice-O-Matic Reviews/   DISCARD #spam rule No slice o-matics

/^From:(.*)Your Free iPad/   DISCARD #spam rule No thank you

/^From:(.*)user005@badspammerdomain.com/   DISCARD #spam Known spammer address

/^From:(.*)Tarot Reading/   DISCARD #spam rule No Tarot reading

/^From:(.*)someaccount@yahoo.com/ REDIRECT ceo@domainexample.com #redirect all messages from this address

Section V - FAQ's

Question: I want to implement header_checks of my own, will Zimbra Support officially support custom header_checks?
Answer: No. However, you are free to add your own header_checks.

Question: I noticed Zimbra uses /opt/zimbra/conf/postfix_header_checks.in, can I edit this file?
Answer: I would suggest if you are wanting to use your own header_checks, keep your header_checks files separate; header_checks for Zimbra, and your own custom header_checks file.

Question: I noticed you are using "DISCARD" in your examples, why are you not using "REJECT"?
Answer: Because using "DISCARD" means the MTA will delete the message; which is what I want given the regexp syntax. The "REJECT" notation will let senders know that their message was rejected, and the MTA refused to deliver their message.

Question: I've added a header_check rule, but it's not working, what do I do?
Answer: Postfix does a good job notating why a specific header_check rule didn't work. Check the /var/log/zimbra.log file.

grep warning /var/log/zimbra.log


Question: I noticed in your examples you are using #spam rule, why?
Answer: Easy grepping of the /var/log/zimbra.log file.

grep "spam rule" /var/log/zimbra.log


Question: Are there any examples on the Internet?
Answer: Yes. Just search for "header_checks by example"

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