Spyderserve Web Development
Being a website hosting company, one of the main reasons that we send emails from our servers is to notify our developers and administrators about an issue (hopefully before the end user sees anything wrong). The only issue with this is when a problem that spawns a lot of messages comes up, the mail queue can fill up very quickly leaving the developers and administrators getting messages for days or sometimes weeks after the issue is fixed. Here are a few commands to clear this cache on the server:
Use this command to list any messages that are currently waiting to be sent:
exim -bp
This command can be used to delete a specific message:
exim -Mrm {message-id}
This command is useful to clear the entire queue:
exim -bp | exiqgrep -i | xargs exim -Mrm
Source: http://www.cyberciti.biz/faq/exim-remove-all-messages-from-the-mail-queue/
Additional Commands: http://bradthemad.org/tech/notes/exim_cheatsheet.php