We found in our ZCS509 (OE) has this kind of message recently and could someone advise what's the cause? and how to fix it?
Jul 19 08:32:15 ms1 postfix/smtp: 8C7A8367C270: to=<firstname.lastname@example.org>, relay=xxx.xxx.xxx.xxx[xxx.xxx.xxx.xxx]:25, delay=19999, delays=19999/0.07/0.01/0, dsn=4.4.2, status=deferred (lost connection with xxx.xxx.xxx.xxx[xxx.xxx.xxx.xxx] while receiving the initial server greeting)
I've searched this forum and found someone fixed this issue by increasing "open file" limit, however, I found ZCS 509 already set the /etc/security/limits.conf for open files correctly. ( I also search my log and there's no "Too many open files" error)
I've already noticed that some articles (not in this forum) said it could be some IPS device caused this issue after mail server was saying EHLO command. (thus disable IPS rule can fix this issue..)
I also found someone said he fixed this issue by adding a MX record for this machine (althouhg he's using pure Postfix , not zimbra).
what I've found makes me confused and could someone here advised for such situation?
Thanks in advance.