sendmail - Deferred local mailer exited with EX TEMPF

Problem

mailq showing:

p68KakUM019887 15952 Sat Jul 9 11:40 MAILER-DAEMON
(Deferred: local mailer (/usr/bin/rmail) exited with EX_TEMPF)

Solution

I had to add the FQDN to sendmail.cw as it only featured the short hostname before. Looks like this caused the lock file to be created. Then execute:

# /sbin/init.d/xntpd stop
# rm /var/mail/username.lock
# rm /var/spool/mqueue/*
# /sbin/init.d/xntpd start