I just started toying with the Drupal Devel Module to try and track down why my CPU usage was skyrocketing again. It seems better suited to help identify slow queries and such, meaning you have to run through every query yourself before you can find the problem.. Didn’t really help find my issue, but I can see how it would be helpful in some cases, and very helpful if you develop Drupal modules (that’s what it’s for).
I had trouble finding any real/helpful documentation for Devel, so I ended up testing/trying all of the different options to see what they do. One option, “SMTP Library” had no info about it that I could find, so I changed the SMTP Library setting from Default to Log Only. Now, a seasoned developer or webmaster would probably know exactly what this setting does, but since I’m a n00b I had to figure it out the hard way.
The only thing I noticed when Changing SMTP Library to “Log Only” is that outbound emails (registration notifications, forgotten password notices, etc) were being written to the watchdog, in full. This seemed like a nifty option to have, so I left it set to Log Only. After a few hours I decided that I’d had enough of the Devel module and disabled it. After disabling I noticed that I was still seeing those SMTP entries in the logs – “great” I thought, this is cool.
It was not until the next day, after I’d received several emails from new members complaining that they were not getting their new-account validation emails that I realized that changing the SMTP Library setting to “Log Only” means just that – all SMTP stuffs would be going into the log and NOT to the SMTP server – meaning, no more outgoing email from the site!.. D’oh! Made perfect sense after I realized this, and I could see how this would be helpful for a developer testing out a new module.. But all it did for me was frustrate members.
To switch the SMTP Library setting back to “default” I had to re-enable the Devel Module and change it back to default. The Devel Module could then be disabled or un-installed.
I hope that this helps other n00bs trying to figure out WTF the SMTP Library setting is for.