Go through this post to troubleshoot mail issues on your server..
Check emails in mail queue
root@server [~]# exim -bp
Count number of emails in mail queue
root@server [~]# exim -bpc
Count number of frozen emails in mail queue
root@server [~]# exim -bp | grep frozen | wc -l
Delete forzen emails from the mail queue
exim -bp | awk ‘$6~”frozen” { print $3 }’ | xargs exim -Mrm
Count emails for an email account/domain
exim -bp | grep username@domain.com | wc -l
Delete emails for an email account
exim -bp | grep username@domain.com | awk ‘{print $3}’ | xargs exim -Mrm ;
Delete emails sent through scripts
exim -bp | grep “<>” | awk {‘print $3}’ | xargs exim -Mrm
Count number of emails in queue for a domain/email account
exim -bp | tr ‘\n’ + | sed -e “s/++/=/g” | tr -d + | tr = ‘\n’ | awk ‘{print $5}’ | sort -n | uniq -c | sort -n
Delete emails for root
exim -bp | grep root@server.hostname.com | awk ‘{print $3}’ | xargs exim -Mrm ;
Hope this helps to troubleshoot mail issues on the server ;-)