Quote Originally Posted by Tintin View Post
email protocol is a long established standard, and I never heard of "incompatibilities" that prevent email servers from exchanging their mail traffic
It was my "simplification" of explanation... For "technical geeks": we have problem with pointer record - PTR - and technical conditions don't allow to change situation on our side, and my exchange by emails with GMX at last 3 months didn't get results - they refused to exclude us from PTR check manually. I have no time for to move our server to another hoster, where is possible to create PTR, so I made decision to "exclude" GMX.