Enable replies via email

Since we plan to move from Google Groups to our discourse instance, I think it would make sense to not regress in terms of features. One feature that “just works” with Google Groups is replies via email, we need to enable that.

One requirement for that is to have a special email account created for the forum and its POP3 settings and credentials.

reference: https://meta.discourse.org/t/set-up-reply-via-email-support/14003

Ok, that’s implemented now.