smtprelay VS mailcatcher

If you have an always on host within the office and accessible to the copiers, even a RPi, there are tons of solutions on Github (ex. https://github.com/decke/smtprelay). A Windows machine I will typically configure hMailServer with MariaDB. For all-cloud, SMTP2Go is really the only solid choice I have found. Others I tried were either more pricey or required a super long key for authentication that copiers did not like.

Yep. I use https://github.com/decke/smtprelay for this purpose.

I use smtprelay, an alternative to the pain in the butt postfix, 3 lines and you are ready to use it to receive email, anything sent to it is automatically "relayed" to your email provider (127.0.0.1) via STARTTLS.

I know about dma, ssmtp, msmtp, nullmailer and https://github.com/decke/smtprelay/, but these don't seem to support queuing and retries.

This is what I use: https://github.com/decke/smtprelay

If you own the server, it might be easier to set up a little smtp client. Or to be more security conscious, a incoming only smtp client like https://github.com/0xERR0R/mailcatcher/ and collapse that dataflow. But pubsub has a monstrous free tier anyway and I also wanted to keep a copy of the emails on gmail which is easier to search

There are lots of ways to do this. Postfix is nice but a little heavy. The simplest and most functional way I've found is https://github.com/0xERR0R/mailcatcher since all it does is forward the emails. You can even use a throwaway gmail SMTP so it doesn't get send to spam

Easy to set up on a rpi/cheap VPS, as long as you have a hostname. And while you're there, look for a short domain name so it's fast to type (on credit card kiosks). You can get cheap short non-standard TLD's like .li. I got a 3 character domain for $5 a year, as short as bit.ly, but just for me

I use selhosted https://github.com/0xERR0R/mailcatcher with ddns domain on my raspberry pi

Maybe https://github.com/0xERR0R/mailcatcher