I have my own email server, using POSTFIX, on a Ubuntu machine at home. The configuration for this includes a "relayhost" directive:-
relayhost=[mail.btinternet.com]:587
Sometimes, when I send an email, it is delayed, with a log entry including:-
...relay=mail.btinternet.com[65.20.50.nn]:587 ....status=deferred (lost connection with mail.btinternet.com[65.20.50.nn] while performing the EHLO handshake)
A few minutes later, it tries again, and succeeds. This time, the log entry includes:-
...relay=mail.btinternet.com[213.120.69.nn]:587.... mail accepted ...
A "dig" of mail.btinternet.com shows:-
mail.btinternet.com. 877 IN CNAME mail.lb.btinternet.com.
mail.lb.btinternet.com. 20 IN A 65.20.50.nn
And sometimes, the A record is:-
mail.btinternet.com. 25 IN A 213.120.69.nn
A "whois" of 213.120.69.nn shows that it is owned by BT.
A "whois" of 65.20.50.nn shows that it is owned by Openwave messaging Ireland.
My emails always get through, but it appears that something is not working quite as it should. If I get a 213.120.69.nn address, it works fine, but, if I get a 65.20.50.nn address, the message is deferred.
