Sometimes it is necessary to remove all frozen messages in exim mail queue immediately. To do this just use:
exim -bpu | grep frozen | awk {'print $3'} | xargs exim -Mrm
command. You can also use specific exiqgrep command for this:
exiqgrep -z -i | xargs exim -Mrm
See also: man exiqgrep
If you want to remove some specific emails from the mail queue, you have to get related message ids first with:
exim -bp
When you know the message id, you can remove it from the queue:
exim -Mrm <message-id>