[Question] Sending email directly to the recipient without a MTA (sendmail, postfix) and without third-party services

[collimarco]

Hello,

I am doing some research online and I can't find any pure Ruby implementation that attempts to deliver the email directly to the recipient. Every gem that I find tries to deliver the email to a MTA (sendmail, postfix) or to a third-party service (Sendgrid, Mailgun, AWS SES, etc.).

I understand the problem with retries, but that could be easily implemented with Sidekiq if we had a gem that attempts to deliver the emails directly.

Also we can implement the DKIM signature etc. in pure Ruby, without an external MTA.

So the question is: can you use this gem to deliver directly to the recipient (without a MTA and without third-party services)?

Have you ever tried that?

Otherwise, what is the missing point? What prevents us from doing that?