The discussion revolves around POP3 authentication with CRAM-MD5. hexa is looking to authenticate using this method but finds that the configuration does not support it. mpalmer explains that CRAM-MD5 is not supported in the Net::POP3 class used by Discourse and suggests that an alternative solution would be to forward emails to another MTA. hexa expresses interest in this alternative solution, and mpalmer later mentions that they will write a blog post on this topic. The blog post is eventually published, and mpalmer shares a link to the documentation on direct-delivery incoming mail, which can be used as an alternative to POP3 polling.
Hi,
it’s me again, from CRAM-MD5 Authentication for mail.
I now need to authenticate to POP3 with CRAM-MD5, but the configuration does not expose that option.
2016-07-23 23:37:48 pop3-login: Info: Disconnected (tried to use unsupported auth mechanism): user=<>, method=PLAIN, rip=82.*.*.*, lip=78.*.*.*, TLS, TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)
Best regards, hexa
I think you’re doomed this time. I can’t even find support for CRAM-MD5 in the Net::POP3 class which Discourse uses, let alone any way to configure it within Discourse. As an added bonus, there don’t appear to be a thundering herd of alternate POP3 libraries for Ruby which we could switch to to provide CRAM-MD5 support.
Short of you doing a lot of coding to add CRAM-MD5 support to Net::POP3, and providing a patch to Discourse to add a tickbox to use that support, I think you’re out of luck here.
Alternately, do you have the ability to forward e-mails sent to your incoming address(es) to another MTA? I’m on the hook for a blog post (and associated docker container) about how to do direct-delivery incoming e-mail (obviating the need for POP3 polling at all); if that would work for you, I’ll get that post out ASAP and you can switch to that.
Yeah, sure. That sounds great!
Hey, did you have a chance to write up how to do that yet? I’d like to get that setup as well.
andi-
No, I haven’t written that up yet. Rest assured it’s still on the todo list, now with two votes next to it. 
For anyone who is interested (and a little bit daring), the direct-delivery construction kit is now available for your amusement. Documentation in this howto topic.