Sometimes a server can get banned maybe because of a client’s misuse or a hack or a weak password or maybe… there are many reasons. You can even get listed in those private lists of unwelcome senders and outlook.com stops talking to your server.
In those cases it would be very useful to have a preconfigured SMTP server so it can be instantly used in case of failure.
I was thinking about mimicking the dns-cluster behaviour.
How exactly should that work?
Personaly I don’t see any reason for a smtp cluster. Sending mails to outlook.com/O365 or gmail is always a bit tricky. If you want to stick on reliable delivery, you can use smtp providers like mailgun, amazon ses and so on - they will take over the whole work.
You could also build a own smtp cluster using mailcleaner or similar software, even a easy exim/postfix installation would work.
It would be something like this:
“Slave server” (or Relay)
v-add-user USER PASSWORD EMAIL
v-generate-api-key
“Master server”
/usr/local/hestia/bin/v-add-remote-smtp-server server 8083 api_key
All accounts in Master server should work in “slave server” (or Relay Server)
In case of need, allow a panel option to send all outgoing mails through XXX Relay Server.
PTR records should be updated too…
That would also work wonders for me. Easy out of the box one click install SES or Mailgun…
I dont see any need for such a function, as already written you can build a relay cluster on your own and/or use external providers.
The problem above is also: When should the server take the decission, to send over its slave? Something which probaly only a admin can decide, then better solve the issue than auto shift over to another server.
Well this function is one of the biggest pains of email hosting. And the fixes are already published in this forum.
It is not needed but highly convenient to people like me. I know that maybe Hestia is not intended for people with my lack of knowledge but this kind of easy things can make Hestia better than Plesk.
Just a “toggle” switch button in the backend would suffice. No automatic behaviour.
So you can instantly switch back and forth and test and be confident that everything will work.
If you keep editing 3 files and stopping and starting services you may make a mistake. If the panel already has a bulletproof system. It would be very convenient.
From the view of a sysadmin: there is no need for this function.
Just a side note: I even didnt found this function in the otherwise so function-overloaded cpanel 
.
You can do it with Exim config …
We are considering the possibility to set up and external smart host / smtp server. On domain / server level. However I don’t see the need for it for an option for a manual / automatic switch…
Any advance in that direction is very positive in my opinion.