Hello,
I would like to have more options for configuring failover delivery.
For example, I think the options in Forimail aren’t bad:
Select another relay (backup relay) that you want to use for failed deliveries. Then specify how long the undelivered email should wait in the normal queue before trying the backup relay.
You can also specify which types of failed connections the backup relay should take over and retry:
DNS failure: failed DNS lookups
Temporary failure from remote MTA (4XX reply code)
Permanent failure from remote MTA (5XX reply code)
Network failure – connection
Network failure – other
Source: Configuring mail settings | FortiMail Appliance and VM 8.0.0 | Fortinet Document Library
Background is this github discussion: Failover delivery not working as expected · stalwartlabs/stalwart · Discussion #2848
I still have the problem with telekom and would love the option to send mails to another mail provider if a permanent error ouccurs.