I have a server which is used purely for outbound email. I would like opendkim to sign every email going through, assuming it has a signing table entry. However, I can't seem to find any documentation for the correct MTA value I need, or any instructions on how to find it (I'm using Postfix).
Originally I had it set to the hostname, but I'm getting messages like the following in the log, which I find confusing as it shows no match, but lists matching values.
no MTA name match (host=my.full.hostname, MTA=my.full.hostname)
At the moment I have the MTA setting commented out, but it is currently only signing emails from authenticated users. I ideally need it to sign anything coming from an allowed relay source - without having to duplicate every single relay into the trusted/internal list.
If anyone has a similar issue it seems to be working if I configure opendkim to use a file for the MTA name rather than providing it directly as a string. (According to the documentation either should be equivalent)
MTA file:/path/to/mta-list.txtmta-list.txt:
my.full.hostname