Store and forward while email server off-line

[jake_g]

Dear All,

Question: can PMG can Store and forward email, if our mail server is off-line?

Reason I ask is that our email server will be off-line for a day, while our core network switches are being replaced.

Our PMG virtual machine is in a DMZ directly connected to our firewall, so it will still be able to receive incoming emails.

The PMG system has 9.3G free disk space, which is easily sufficient to store the incoming mail.

However, we use the Recipient verification built into postfix to prevent backscatter, thus PMG contacts our email server to confirm email addresses.
Does PMG cache these email addresses, if so how long is the cache valid for?

Are there any other PMG settings that would break store / forward?

Would it be safer to disable incoming email to PMG while our email server is off-line?

many thanks

Jake

 

[Stoiko Ivanov]

Question: can PMG can Store and forward email, if our mail server is off-line?

put shortly - yes - but that's a general functionality of SMTP - if a destination server is not reachable any good SMTP server will queue the mail and try resending it at a later point.
Postfix (the MTA used by PMG) by default queues mails for up to 5 days - see https://www.postfix.org/postconf.5.html#maximal_queue_lifetime

The PMG system has 9.3G free disk space, which is easily sufficient to store the incoming mail.

even if it runs full - postfix would reply with a temporary error (4XX), and the sending server should then try to resend the mail later (also for a while)

Does PMG cache these email addresses, if so how long is the cache valid for?

yes - caching happens - for postive results the cache-time is 31 days - for more details see:
http://www.postfix.org/ADDRESS_VERIFICATION_README.html#caching
and http://www.postfix.org/verify.8.html (for the parameters you can tweak regarding caches)

if you want to adapt the postfix config in PMG use the templateing system:
https://pmg.proxmox.com/pmg-docs/pmg-admin-guide.html#pmgconfig_template_engine


I hope this helps!

 

[jake_g]

Hi Stoiko,

Thank you for confirming that PMG will do all of those things.

Very nice to know that everything will be OK while our internal mail server is off-line

Have a great day,

Jake