Thursday afternoon we started receiving emails from folks who were having trouble retrieving password reminders, and new registrations that were not receiving their confirmations.  We had been making modifications to our mail server configuration for SPAM control, so thought briefly that we might have introduced a problem.  However, quick testing revealed that the problem was localized specifically to emails sourced from our production web server.

It turns out that in our infrastructure we had neglected to add new IP ranges to the permissions list for our mail server.  So in our planned IP cutover ( which has been pretty seamless ), this step was neglected which resulted in our own web server being banned from SMTP usage.  This was not discovered internally immediately, because email within the domain ( i.e sent from an @dotnetnuke.com address to another @dotnetnuke.com address ) is generally still permitted as legitimate traffic ( it doesn't invoke SMTP ).

We apologize for any inconvenience that this may have caused and have added measures to mitigate any future occurrence.  The problem was resolved within 24 hours.

Cheers