Operations grimoire/Mail/DKIM

Mails are signed with OpenDKIM, an open-source implementation for DKIM.

Add a domain

To create a key with unium as DKIM selector for <domain.tld>:

$ mkdir /usr/local/etc/opendkim/keys/domain.tld
$ cd /usr/local/etc/opendkim/keys/domain.tld
$ opendkim-genkey -s unium -b 2048 -d domain.tld
$ chown opendkim unium.private
$ cd /usr/local/etc/opendkim
$ make clean all

Test

Send a mail from to another mail server.

You should see a DKIM pass.

You can also from a mailbox for this domain send a mail to check-authverifier.port25.com

Troubleshooting

Can't load key from … Permission denied

Keys must belong to opendkim user.

$ chown opendkim /usr/local/etc/opendkim/keys/*/*.private

DKIM must succeed: as long as this isn't fixed, Postfix won't send mail for this domain.