List mails in the queue:

$ exim -bp

View headers of a mail:

$ exim -Mvh <mail-id>

View body of a mail:

$ exim -Mvb <mail-id>

Remove a mail from the queue:

$ exim -Mrm <mail-id>

Remove all frozen mails in the queue:

$ exiqgrep -z -i | xargs exim -Mrm