Our Zimbra accounts has external POP3 accounts configured for downloading emails from external mail server. The problem is out of offices doesn't work for e-mails delivered via these external POP3 accounts. E-mails are delivered to the users inboxes but the out of offices are not sent. I've checked in the mailbox.log that Zimbra is not even try do sent any OOO in response to these e-mails. Please help.
Zimbra version: 8.8.8 Patch 7
Edit:
This is the answer I got from Zimbra support:
Since you have set an external account and mail is not hitting the Zimbra server so the out of office is not generating because it is not hitting Zimbra MTA server which is reason OOO is not working.
They said that they "will look forward to such feature in our future release" but I wouldn't count for this...