Milter to add SMTP AUTH Authentication-Results field to self-sent mails.
Mails from authenticated clients will usually be processed differently by
milters such as OpenDKIM and OpenDMARC. OpenDKIM will sign the mail instead
of verifying it, and OpenDMARC will simply ignore it. As a result, mails
sent by authenticated clients will not have any Authentication-Results
fields in their header. For outgoing mails, they will be verified by their
recipient, but for local mails, they will stay as is.
Having a mail without any Authentication-Results field can confuse MUAs
such as FairEmail, that use it to display the authentication status of a
mail.
To fix this issue, homard adds a SMTP AUTH Authentication-Results field
as described by RFC7601 § 2.7.4 to the header of mails sent by authenticated
clients or sent from localhost. This is usually enough for MUAs to consider
the mail as fully authenticated (as it is)
In this screenshot, the second mail is sent with homard whereas the first is not.
Postfix is run in a chroot in Debian, so it is needed to adapt the default configuration. Create a new directory for the UNIX socket in Postfix's chroot with the correct permissions, for example with systemd-tmpfiles:
#/etc/tmpfiles.d/homard.conf
#Type Path Mode User Group Age Argument
d /var/spool/postfix/homard 0750 homard postfix - -Then:
sudo systemd-tmpfiles --create
Set the ListenURI in homard's config file:
# /etc/homard.conf
ListenURI = "unix:///var/spool/postfix/homard/homard.sock"Add homard to postfix's milters in /etc/postfix/main.cf:
smtpd_milters =
local:opendkim/opendkim.sock
local:opendmarc/opendmarc.sock
+ local:homard/homard.sock
non_smtpd_milters =
local:opendkim/opendkim.sock
+ local:homard/homard.sockAdd postfix to the homard group:
sudo adduser postfix homard
And finally restart both services:
sudo systemctl restart postfix homard
The name kind of means HOMe Authentication-Results Daemon, but it was mostly chosen because it means "lobster" in French and ends with "ard".