When a server/VM mail queue size is large:-

1. Go to WHM -> Mail Queue
- Analyze (click on magnifiying glass) some of the repetitious / suspicious
mail to determine whether it's spam (google subject line / from / some
content to verify)
- Also determine the email account used/hijacked to propagate the spam
(Click on 'Show Control Data' when viewing a queued message)
- If confirmed, see if the From header is the same (normally it is), then
you can do bulk removal as follows:-

i) SSH to server

ii) Verify the spam search pattern by sender in queue:- # exiqgrep -f
'sender@address.com'

iii) If confirmed, get the queue IDs:-
# exiqgrep -i -f 'sender@address.com'

iv) If list looks OK, now delete all the spam mails from queue:- # exiqgrep
-i -f 'sender@address.com' | xargs exim -Mrm

v) Sometimes there are backscatter (bounce messages back to the hijacked
account) or spam sent to one particular address. For this, use spam search
pattern by recipient in queue:- # exiqgrep -r 'recipient@address.com'
# exiqgrep -i -r 'recipient@address.com'
# exiqgrep -i -r 'recipient@address.com' | xargs exim -Mrm