[exim] Don't send certain emails

Hi,

We currently use Exim because it allows us to filter emails to capture a
'job code' users must include in the first line of any email. We use this
information to keep track of how many emails we send per job, and their size
(in kB), to allow for billing. All this is achieved by using filtering to
parse emails through a custom Python script.

The system works well, except that Exim will send an email even if it
doesn't have a job code.

Is there a way to ensure that if no job code is included, the email will not
be sent?

Thanks,

Anthony