So my MySQL tuning above doesn't resolve entirely the problem, it just makes the POP/IMAP delays happen way more less, so there's definitly room for improvement.
I still get a couple mysql errors:
2024-08-26 10:07:45 7 [Warning] Aborted connection 7 to db: 'grommunio' user: 'grommunio' host: 'localhost' (Got timeout reading communication packets)
2024-08-26 10:07:45 9 [Warning] Aborted connection 9 to db: 'grommunio' user: 'grommunio' host: 'localhost' (Got timeout reading communication packets)
2024-08-26 11:07:45 54 [Warning] Aborted connection 54 to db: 'grommunio' user: 'grommunio' host: 'localhost' (Got timeout reading communication packets)
2024-08-26 12:07:45 89 [Warning] Aborted connection 89 to db: 'grommunio' user: 'grommunio' host: 'localhost' (Got timeout reading communication packets)
2024-08-26 13:07:45 105 [Warning] Aborted connection 105 to db: 'grommunio' user: 'grommunio' host: 'localhost' (Got timeout reading communication packets)
2024-08-26 14:07:45 132 [Warning] Aborted connection 132 to db: 'grommunio' user: 'grommunio' host: 'localhost' (Got timeout reading communication packets)
I'll try a bit more tuning. Currently trying to raise connect_timeout
.