Install mail servers

From The Network People, Inc. - Wiki

Step 7: Install Web/POP3/IMAP servers

Install either of the following IMAP & POP3 servers (see note):

toaster_setup.pl -s courier
toaster_setup.pl -s dovecot

Mail Toaster Install Steps
Prep.	perl	Mail Toaster	ports	config files	programs	filtering	logging	cron jobs	test

See the Courier_vs_Dovecot page for more info.

If you are switching from Courier IMAP, there are some Migrating to Dovecot issues.