Your log (NDR) says:
Sender address rejected: not logged in
I don´t know how your antispam works, but it seems that it does no authentification when the mail is passed to your iredmail server.
If you can´t teach your Antispam to authenticate, you can deactivate the check in iredmail (see http://www.postfix.org/postconf.5.html# … _mismatch)