Is there a reason why DKIM signs every mail twice

Question

I've configured my postfix/amavisd-new/spam-assassin setup after this tutorial https://help.ubuntu.com/community/Postfix/DKIM. But now the problem is that all mails I send are double signed with two DKMI Headers, one before and one after the mail is sent to amavisd-new. How can I prevent this behavior?

Solution

to disable milter processing after amavis, add to your master.cf in the after-amavis section

127.0.0.1:10025 inet    n       -       -       -       -       smtpd
[....]
-o smtpd_milters=

if you want to run the milter after amavis, set the smtpd_milters= configuration option in main.cf to an empty string and add the inet:localhost:8891 configuration to master.cf instead:

-o smtpd_milters=inet:localhost:8891

Comments

[tanascius]

Possible problem is using opendkim and rspamd, when rspamd enables the dkim-signing module ... :( happened to me

[Lexib0y]

Should this solution also work with spamassassin? (asking because it failed on my server)

[B. Shea]

Which is best practice? After Amavis? @Lexib0y - spamassassin is run via amavis(-new), normally. So, the answer is yes. Try 'after amavis is run' in this answer. Works for me, anyway.