IMAP/Exim failing on cPanel server

If you are on cpanel server you might encounter errors related to imap. Below given is an example of error you might encounter.

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Service Check Method: [tcp connect]

Failure Reason: TCP Transaction Log:
<< * OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT
THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS] Courier-IMAP ready.
Copyright 1998-2011 Double Precision, Inc. See COPYING for distribution
information.
>> A001 LOGIN
__cpanel__service__auth__imap__rJgtrLJMaRsNRJAy1xrY3gjTDNA852bfXgTyA8ttThGb3PWtney7UFHfeEuyP9bg
EFRrpZNcstXly7t6cq5gQmthW7w4Qd4xlUeldCDdm67tiIsq_6efRRsLOy3WpZA3
<< * BYE Temporary problem, please try again later
imap: ** [* BYE Temporary problem, please try again later != A001 OK]
: Died at /usr/local/cpanel/Cpanel/TailWatch/ChkServd.pm line 541, line
2.
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Error message logged in ” /var/log/maillog”.

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/var/log/maillog:Jan 30 20:10:04 s307 imapd-ssl: authentication error: Input/output error

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The issue can be fixed by increasing the authentication daemons for courier in the server.

Follow the below given steps:

Login to WHM

Service configuration

Mail server configuration

Number of authentication Daemons (Increase the current value to higher).