Emails from a Plesk server can not be sent using a mail client, for example, Outlook:
Your IMAP server wants to alert you to the following: Inotify initialization error
Courier IMAP server is used for IMAP/POP3 delivery.
/var/log/mailloglog file the following errors can be found:
plesk courier-imaps: Failed to create cache file: maildirwatch ([email protected])
plesk courier-imaps: Error: Too many open files
Insufficient value for per-userid limit of inotify file descriptors.
Connect to the server via SSH.
Check the current per-userid limit of inotify file descriptors:
# cat /proc/sys/fs/inotify/max_user_instances
Increase this value to a greater one via the command below, for example to 200:
# echo "fs.inotify.max_user_instances=200" >> /etc/sysctl.conf
Note: Rough metric is the number of concurrent IMAP sessions multiplied by 4.
Apply changes by executing the command:
# sysctl -p
Restart Courier-Imap services:
# systemctl restart courier*