We recently upgraded to 2.7.3 and have encountered an issue with emails being processed through cronjobs very slowly (approximately one every 1.2 seconds). Throughout the day we have an increasing amount of emails, which then causes a snowball effect, cron takes longer to finish, which means more emails need to be sent, which means it takes longer, etc.
We use a SMTP server for our mail relay, and have for the last 6 years of moodle usage without issue. I've reached out to the team that supports the server and they're confirming there's no load issue on their end, which is confirmed by the fact that when I tail the logs on our side, each "Processing user" line shows up at a little bit over 1 per second.
We have 4 load balanced webservers all running cron (each server runs it every 4 minutes, but offset by 1 min each, so 1st webserver runs at *:00,*:04,etc. 2nd webserver at *:01,*:05, etc.).
Has anyone else noticed large performance degradation in forum email processing with 2.7? Is there some configuration setting I missed or optimization I am unaware of?