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Accepted Answer
In this situation there are a few options to consider:
1.) As you mentioned, you could run postfix or another MTA on the host.
2.) You could choose from several existing mail server docker containers, map your ports and use that for processing messages
3.) You could use a transactional mail provider like SendGrid or MailGun to send messages. Personally I choose to use this option as most providers have a free tier and it takes the work of maintaining email services off my shoulders.
4.) You could run a separate server as a mail server which could serve several hosts running docker containers.
Hmm… #2 is a good point. I didn’t even think to look for one of those. [face-palm]
That being said, I think I will end up taking the mail provider option. Unless I missed something SendGrid is only free if you’re hosting your app on Google’s AppEngine, but MailGun is definitely looking like a good option.
Thanks, Ryan!