I’ve just had to delete a bunch of messages from an Exim queue and I found this to be useful:

# exiqgrep -f billg@microsoft.com

Will print out details for any messages from that address.

To delete any messages from a person use the f as well as the i flags to print out just the message id, this can neatly be piped to xargs:

# exiqgrep -i billg@microsoft.com | xargs exim -Mrm