outgoing smtp choose server based on From address

Question

I use an email client called Alpine. Currently I start it in one of several different modes in order to specify the outgoing SMTP server based on what I'm doing, in particular the From address that I wish to use.

What would be much more convenient is if I could simply direct Alpine to use my own SMTP server (on my laptop), which in turn would choose a relay server based on the From address of each message I'm sending.

I am hoping someone is already doing this (it seems like it should be a common need given recent tightening of restrictions on accepting mail) and that it is not complicated.

(As a bonus, I'd also like to be able to start Alpine in a mode which uses a local server that waits until Monday morning to send out messages.)

Here is possibly the same question: Changing SMTP authentication in mutt based on From e-mail address, but it is old and so are references on esmtp – I'm not sure esmtp is up to date with modern security protocols, etc.

At the risk of possibly splitting this question in two, I cannot find out how to call a server like esmtp from Alpine, ie instead of giving it a remote server address, etc, I want to spawn a local process (each email?? Or do I run esmtp once?) — CPBL, Jul 09 '20 at 17:42

score 0 · Accepted Answer · edited Jul 15 '20 at 18:42

Answer for Alpine email client

Recent versions of Alpine are compiled for Ubuntu with many of the available patches, i.e., enhancements, and these include a feature called "smtp-rules". It's not perfectly well documented, but here is what the .pinerc section looks like for me. It handles email addresses from my employer, from my alma mater, and from two Gmail identities:

# Unfortunately, using gmail's SMTP servers require setting up 2-factor authorization,
# which then allows you to get an "app password" for each account, which can be used
# by Alpine. Instead of doing this, for now I'm using MIT's, which is changing but
# currently letting through my gmail identities
smtp-rules= _FROM_ == {[email protected]} => _SMTP_{smtp.office365.com:587/tls/[email protected]}
smtp-rules= _FROM_ == {[email protected]} => _SMTP_{outgoing-alum.mit.edu:465/ssl/user=me}
smtp-rules= _FROM_ == {[email protected]} => _SMTP_{outgoing-alum.mit.edu:465/ssl/user=me}
smtp-rules= _FROM_ == {[email protected]} => _SMTP_{outgoing-alum.mit.edu:465/ssl/user=me}

For other clients, or another way using Alpine

I haven't tested esmtp, since the above works nicely, but this seems to be an alternative:

Install esmtp
Set the smtp-server field to the executable, /usr/local/bin/esmtp

Put something like the following in your ~/.esmtprc file:

identity [email protected]
    hostname mail.server.com:25
    username "joe"
    password "secret"
    starttls enabled
    default
identity [email protected]
    hostname smtp.gmail.com:587
    username "[email protected]"
    password "secret2"
    starttls required

Reference for the esmtp part: Send mail with eSMTP for a simple, single-user system - TechRepublic.

outgoing smtp choose server based on From address

1 Answers1

Answer for Alpine email client

For other clients, or another way using Alpine