Whats happends to Emails, when target Mailserver is offline ?

[Supaman]

Hello,

i am planning to run the following setup:

- PMG on a VPS at external Hoster
- Mailserver OnPremise

Except occational maintanance, the PMG will be up all the time. The Mailserver could be sometimes offline for several hours (up to one working) due to internet failure.

The question is: what will happend to emails in this case? The PMG will recieve emails, but could not deliver them to the mailserver. will they stay in qeue until mailserver is back, or did they get bounced back to sender?

regards,

Supa

 

[Onslow]

Hello.
Unless messages to the "server on premise" are treated a special way, they wiil be queued for "maximal_queue_lifetime" (default: 5d).

"Consider a message as undeliverable, when delivery fails with a temporary error, and the time in the queue has reached the maximal_queue_lifetime limit."

https://www.postfix.org/postconf.5.html#maximal_queue_lifetime