I would like to write an elixir/phoenix application that simply serves as an email router – I want it to be able to receive emails, examine who they are from, and then forward them on to whoever they are supposed to go to based on a lookup table I will maintain.
In addition, I don’t want to have to pay for an external service such as SendGrid or some other third-party email solution.
I guess that gen_smtp is what people will advise me to reach for. Since I want to work in Elixir, it looks like I should try Mailman, since it advertises itself as an Elixir wrapper around gen_smtp.
So I’m curious whether I can use Phoenix 1.6 but swap out Swoosh for Mailman. Also, any advice about how I should go about this? Mailman doesn’t really have any docs to speak of. Or should I just try and stick with Swoosh, since I see that it also pulls in gen_smtp in it’s own mix.exs file?
Swoosh supports smtp transport too; I use it every day.
For what you are trying to do though, I think popular SMTP servers like exim4 already provides sophisticated rule based forwarding functionality. Polling the mailbox then forward the mail seems like a lot of work; plus I don’t think Swoosh can forward mails in a totally loss-less way. I am not sure about mailman but I would think any time you parsed the mail and re-serialize it out there will be some lost info and additional artifacts. In contrast, exim4 forwarding treats the mail blob as is.
@derek-zhou thanks – this seems like valuable advice.
But why would I have to poll the mailbox? It seems to me that if I have gen_smtp running, then I can just write rules that will react whenever an email is received.
As for parsing the email, the only information I’m interested in is the FROM and TO fields – those will serve as the keys to determine where the email should be forwarded. I would prefer to leave the rest of the email untouched.
I’m curious why you think polling would be involved here. Just as a web server just sits around waiting and only responds when it receives a request, shouldn’t I be able to have an SMTP server with gen_smtp that just sits around waiting, but reacts instantly as soon as an email is received?
I am not sure gen_smtp can act as a full fledged smtp server; there are a lot of nuances in real world smtp. In any event the full smtp functionalities are not exposed via swoosh.
