Use the ssh command below to remove all messages from and to a users domain. This will help to resolve issues with your exim smtp mail queue. You can adjust the search string accordingly.
The command below will delete all emails TO domain.com:
# exiqgrep -i -t domain.com | xargs exim -Mrm
The command below will delete all emails FROM domain.com:
# exiqgrep -i -f domain.com | xargs exim -Mrm