SymptomsCustomer cannot connect to their qmail mailbox using IMAP client, the error message says about incorrect username or password.
The attempt to log into mailbox using the telnet utility fails with the error message Temporary problem as in the example below:
# telnet qmail01.provider.com 143
Connected to qmail01.provider.com (192.168.1.101).
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 NAMESPACE QUOTA ACL UIDPLUS CHILDREN IDLE] Courier-IMAP ready. Copyright 1998-2011 Double Precision, Inc. See COPYING for distribution information.
a001 LOGIN email@example.com p@$$w0rd
* BYE Temporary problem, please try again later
CauseThe service courier-auth may hang on qmail server(s).
Log into qmail server(s) and try to restart the service courier-auth:
# /etc/init.d/courier-auth restart