https://github.com/bootrino/arniesmtpbufferserver/blob/master/arniesmtpbufferserver.py

Here's the github repo:

https://github.com/bootrino/arniesmtpbufferserver

It's MIT licensed.

Arnie is a server that has the single purpose of buffering outbound SMTP emails.

I wrote Arnie because I got frustrated using complex queueing systems simply to buffer outbound SMTP emails. I'd rather spend time writing this than spend the same time debugging Celery configuration.

A typical web SAAS needs to send emails such as signup/signin/forgot password etc.

The web page code itself should not directly write this to an SMTP server. Instead they should be decoupled. There's a few reasons for this. One is, if there is an error in sending the email, then the whole thing simply falls over if that send was executed by the web page code - there's no chance to resend because the web request has completed. Also, execution of an SMTP request by a web page slows the response time down of that page, whilst the code goes through the process of connecting to the server and sending the email. So when you send SMTP email from your web application, the most performant and safest way to do it is to buffer them for sending. The buffering server will then queue them and send them and handle things like retries if the target SMTP server is down or throttled.