For a couple of months, we have been chasing a problem that appears as though forum posting email notification messages are not being sent. Some people receive them and some people don't. We were able to find some folks to help us with the diagnostics, and they found that the problem was related to the fact that Moodle sends "bare line feeds" (not preceded by a carriage return) in the notification email, which is against the SMTP email handling standards. Here is a link that describes the problem:
Here is a brief log entry (failed message) supplied by the diagnostic team, along with their comments when we told them notification worked with a Yahoo address:
============= BEGIN DIAGNOSTIC COMMENTS =============
2007-10-24 17:58:00.491020500 tcpserver: pid 11441 from 22.214.171.124
2007-10-24 17:58:00.491339500 tcpserver: ok 11441 server272.com:126.96.36.199:25 :188.8.131.52::35361
2007-10-24 17:58:00.719394500 11441 < MAIL FROM:<MoxleyD@health.missouri.edu>
2007-10-24 17:58:00.771704500 11441 < RCPT TO:<firstname.lastname@example.org>
2007-10-24 17:58:00.881997500 11441 > 451 See http://pobox.com/~djb/docs/smtplf.html.
2007-10-24 17:58:00.882001500 tcpserver: end 11441 status 256
We are running QMail as a mail agent. Bare LFs are considered an error by this agent as they are violating the SMTP mail sending standards. Most likely Yahoo is using a different mail agent that is not considering this as an error. Please note that we can't change the behavior of QMail on our side. You will have to correct the format of the message that you are trying to send. You can also contact the developers of the software that you are using and notify them about the issue.
============= END DIAGNOSTIC COMMENTS =============
We are not sure how to fix our Moodle configuration to change this. It could be that it is something that needs be changed in the Moodle code. Would someone be able to help us with some direction on this?