Thanks for the bug report! I agree DMARC and even ARC support would be good to have here. Unfortunately, as with libspf2, libopendmarc is a universe package and would be difficult to justify having as a build dependency. It's possible this could be changed though. An alternative to this may be to use opendmarc alongside exim4 to support it like Ubuntu does with spf-tools-perl. Either way I'll see what we can do to support this.
Thanks for the bug report! I agree DMARC and even ARC support would be good to have here. Unfortunately, as with libspf2, libopendmarc is a universe package and would be difficult to justify having as a build dependency. It's possible this could be changed though. An alternative to this may be to use opendmarc alongside exim4 to support it like Ubuntu does with spf-tools-perl. Either way I'll see what we can do to support this.