Fix courier imapd.pem error PEM routines no start line

Error courier imapd.pem file

tailf /var/log/mail.log
imapd-ssl: couriertls: /etc/courier/imapd.pem: error:0906D06C:PEM routines:PEM_read_bio:no start line

How to fix

vim /etc/courier/imapd-ssl

Make sure dhparams.pem added on the file

##NAME: TLS_DHPARAMS:0
#
# TLS_DHPARAMS - DH parameter file.
#
TLS_DHPARAMS=/etc/courier/dhparams.pem

Restart courier-imap-ssl

/etc/init.d/courier-imap-ssl restart