Postfix

Postfix is a mail server, just enter the following command to flush the mail queue:

postfix -f

Other cleaning mails commands:

postsuper -d ALL Delete differed mail queue messages

postqueue -f Process queue. Or: postfix flush

postcat -vq XXXXXXXXXX > themessage.txt save mail to file

mailq display queue or: postqueue -p

postsuper -d deferred mail clear queue