I'm experiencing issues sending emails to, in particular, gmx addresses. The error received indicates a bad PTR record:
Action: failed
Final-Recipient: rfc822;
[email protected]
Status: 5.0.0
Remote-MTA: dns; mx00.emig.gmx.net
Diagnostic-Code: smtp; 554-gmx.net (mxgmx015) Nemesis ESMTP Service not...