Sendmail problem: Mail is getting stuck on /var/spool/mqueue

1. Find out what version of sendmail is running by typing sendmail -d0.1
2. Look at the version by running the above command. If sendmail version 8.9.x then edit /etc/sendmail.cf and if
version 8.11.x then edit /etc/mail/sendmail.cf
3. Search for DS in sendmail.cf then add bracket [ ], for example: DS[d02smtp01.southbury.ibm.com] and by adding
the bracket you are forcing to look at CNAME instead of MX record name
5. Then kill the sendmail daemon kill -9 sendmail_pid (you can find senmail_pid by typing ps -ef | grep sendmail)
6. Then start the sendmail daemon /usr/lib/sendmail -q15m (If it is sendmail cleint) or /usr/lib/sendmail -bd -q15m
(If it is sendmail server)
7. You will see all the mail queues are getting cleared from /var/spool/mqueue directory after few minutes or just
run the command: #mailq