Yesterday, I made my first post in a long while subscribing to the thread and asking for instant notification. A reply was made but no notification. Since I am also my mail server's administrator, I was able to see what was going on. The notifications were getting to my mail server but were being rejected because the domain (web1.micechat.com) of the sending address ([email protected]) does not exist.
Rejecting mail claiming to be from non-existent domains is a common anti-spam technique in mail servers. To improve the chances of these notifications being delivered, the domain web1.micechat.com MUST exist in the Domain Name System (DNS).
For the admins, here is the redacted log entry from my end (mail server is Postfix):
Nov 19 06:24:03 myserver postfix/smtpd: NOQUEUE: reject: RCPT from unknown[188.8.131.52]: 450 4.1.8 <[email protected]>: Sender address rejected: Domain not found; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<web1.micechat.com>