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I am working on learning how to setup a mail server and have a question regarding the use of mail filters with Postfix.

I am looking at the following guide (as well as a similar guide on the Ubuntu wiki):

https://help.ubuntu.com/12.04/serverguide/mail-filtering.html

It has you install a number of packages:

amavisd-new, spamassassin, clamav-daemon, opendkim, postfix-policyd-spf-python, pyzor, razor

Then, very simple directions are given (which is nice) for setting up ClamAV, SpamAssassin, and Amavisd-new. It is mentioned specifically that SpamAssassin will automatically detect and use pyzor and razor, and that no additional setup is needed for those.

However, there is never any discussion as to how to setup SPF or DKIM, or whether they are automatically setup. Are these also automatically setup and integrated, like pyzor and razor? Or, is additional setup needed?

The Ubuntu Manpage discusses a setup for postfix-policyd-spf-python, as does an Ubuntu wiki page, but neither discusses anything about amavisd-new, spamassassin, or clamav-daemon, and whether or not SPF is automatically setup with those and the postfix-policyd-spf-python package, or whether the setup they detail must be done whether you are using it with those three package or not.

http://manpages.ubuntu.com/manpages/precise/man1/policyd-spf.1.html

Can anyone clarify this a bit?

Thank you.

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That guide is all about filtering spam out of your incoming mail. There's not really any setup required on your system apart from saying you'd like to check SPF and DKIM.

If you invoke that checking, then when your server gets an email from IP address 123.123.456.456 claiming to be from fred@example.com, it will look for a TXT record in the DNS entry for example.com to see if that IP address is listed as a valid source of mail for example.com

DKIM just adds some more complexity on top of this

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