How to Remove all Messages from Mail Queue

To remove all messages use the following command:

# exim -bp | awk '/^ *[0-9]+[mhd]/{print "exim -Mrm " $3}' | bash

Source

Exim Remove All messages From the Mail Queue. http://www.cyberciti.biz/faq/exim-remove-all-messages-from-the-mail-queue/