I was trying to send an email campaign last night. I have recently upgraded to 3.3.1 and haven't had time yet to reconfigure the cron processes to handle thing automatically. So I was using the built in 'Process Queue' functions through the PHPList web pages on our system. I have tried using these things before and it has always kind of confounded me.
So I turned off my screen saver, turned off the computer power saving and sleep modes (set both to 'never'), started up the PHPList Process Queue process and the processing page showed up, feedback appeared, and it started spinning. Great - so far so good. Some emails showed up for people on the list.
This list is somewhat large - about 1000 people. Our email service only allows about 150/hr to be sent, so I have set the Throttle configuration in PHPList accordingly. But how do I get the web page to actually finish processing things? I had left the web page front and center and was the 'in focus' window on my screen. Then I went to bed. It appears that the web page itself timed out - when I checked back in in the morning it still showed the feedback from the first run of processing and when I clicked on something the system made me log in again.