Spam attack, Mailqueue has 1000s + emails

Im trying to clear the mail queue after a spam attack.
but i am getting this error.
running ISPConfig 3.1 on CentOS

#postqueue -f
#postqueue: fatal: Cannot flush mail queue - mail system is down

any suggestions?

 

i have just done this by selective email and it has worked. However, when i look at the mail queue in ispconfig it still shows thousands of email stuck in the queue. when i check with "postqueue -p" there are only a few legit emails left

 

Once you have solved it, please consider using rspamd's rate limit feature. Has saved me a few times already.