How to Speed up courier-imap

Courier-imap allows ONLY 4 connections per IP by default. Although it is due to security reasons, it often limits parallel processing caused by clients.

For example, Thunderbirds, a famous mail user agent, has 10 connections by defaults. If you use its default setting, the error dialog which indicates connection is refused appears.

So if you hope, you can increase the number of maximum connections of courier-imap by specifying in /usr/lib/courier-imap/etc/imapd below:

MAXDAEMONS=40 MAXPERIP=40