If I recall correctly, a lot of MTAs check to see that the PTR of your mail server machine matches the FQDN of your mail server. If they don’t, the connection would be terminated unless some sort of exception is entered in the remote server’s configuration files. I worked for a company that did this very thing and had clients that could send emails to other domains but not the domain of the company I was working before because the PTR <-> MTA hostname check was strongly enforced. Again, IIRC, we had to set up an exception in our postfix configuration at the time because the admins of the sending domain did not want to be bothered correcting this in DNS or even be bothered by creating a proper SPF record.
From: owner-postfix-us...@postfix.org [mailto:owner-postfix-us...@postfix.org] On Behalf Of Dennis Steinkamp Sent: Monday, December 28, 2015 6:16 PM To: postfix-users@postfix.org Subject: myhostname = ptr? Hey there, i read many times that 'myhostname' in the postfix configuration should be the same as the ptr and some say even the same as the mx record. So i played around with it a little bit and figured, that even though i ve set the 'myhostname' to mail.greatserver.com, whereas the hostname of the machine running postifx and the ptr is just greatserver.com, the smtp banner check on mxtoolbox reports everything is fine. I ve read through the smtp banner check description on mxtoolbox.com and it says: "You will get this warning if the name you present yourself as is not in the same domain as the hostname we get when we perform a PTR lookup on your IP Address." So i am asking myself, is it really necessary that the HELO of my postfix server and the ptr are exactly the same? Excuse me if it sounds like a stupid question but i am new to all of this and i just wanna do things right from the start and understand it correctly. So basically if i wanna set myhostname to mail.greatserver.com i have to change the ptr to mail.greatserver.com too to comply with the RFCs and "best practices" or is only the same domain part relevant like mxtoolbox says? Thank you for helping me out. Bye Dennis
