Mail application which allow to choose smtp server I am using Gmail and I have two SMTP settings on Accounts tab (Gmail - Settings - Accounts - Send mail as).  So I get mail on my gmail account, but can choose which SMTP server use to send mail - smtp.gmail.com or my own smtp server.

I am just wondering if there is a mail application which allow me to choose smtp server for each mail I send ?
I had a somewhat similar question about iOS a few months ago and got an excellent recommendation for postfix -- for osx. Unfortunately that answer did not apply to iOS but it may be a useful answer for your purpose!

https://apple.stackexchange.com/a/102708/52358

You want to take a look at the answer by buscar