Figured out, check https://sogo.nu/bugs/view.php?id=4681#c13374
Just need to update/upgrade apt (nightly builds)
@admin, not that when upgrading SOGo from 3.* to 4.* for the default configuration, for Debian and derivatives you need to increase the 'prefork' value from 10 to 20 for a few users.
If not done, sogo put server in high load average and high mem and sogo.log display errors:
Feb 17 21:51:13 sogod [4854]: [WARN] <0x0x55c90293b8c0[WOWatchDogChild]> pid 4866 has been hanging in the same request for 3 minutes
Feb 17 21:51:25 sogod [4854]: [WARN] <0x0x55c90292be10[WOWatchDogChild]> pid 4942 has been hanging in the same request for 2 minutes
Feb 17 21:52:13 sogod [4854]: [WARN] <0x0x55c90293b8c0[WOWatchDogChild]> pid 4866 has been hanging in the same request for 4 minutes
Feb 17 21:52:25 sogod [4854]: [WARN] <0x0x55c90292be10[WOWatchDogChild]> pid 4942 has been hanging in the same request for 3 minutes# cat /etc/default/sogo
# The amount of processes that should be spawned (Default: 3)
PREFORK=20