We can increase the webmail imap connection limit for the connection from same ip address on the Plesk Linux server to avoid the imap connection error because of excessive connection to the imap service from same ip address. To increase the imap connection limit follow the following steps.
Login in to the shell as a root user and open a file “/etc/courier-imap/imapd” in your favorite editor.
nano /etc/courier-imap/imapd
Change the following value as per your requirement, for example we have changed it to the 25 from the default value 8.
From
MAXPERIP=08
To
MAXPERIP=30
Restart the imap service.
/etc/init.d/courier-imap restart
