Can not figure this out, need help

Hello guys,

I can’t figure out how to do this,

I want to make a config for smtp, it’s like this - suppose I know the server name will begin with - I have many different domain names.

I do not want to use Automantic Connection because it’s taking too long to check out and guessing different server connections, I want to create a “Connect to server” manually.

Example: I have 123@domain1 .com - 123@domain2 .com - 123@domain3 .com

how could I write in server name - I tried to write like this:

smtp.input.USERNAME or smtp.<input.USERNAME> - it doesn’t work - I want the config to make a connection like this:

smtp.domain1 .com:587
smtp.domain2 .com:587
smtp.domain3 .com:587

Is it possible to write config like this?

Please, I need help - thank you so much !

P.S: Sorry I had to make a space in domain names because of new user restrictions which I could not post with many links.