It would be Really Nifty (tm) if mail() accepted an 
additional argument in which the email's MessageID 
was 
returned for tracking purposes...

This would make it much easier to track abuse of 
web-pages/sites that provide access to mail() to the 
end-user...

If it's not a 5-minute job, forget it, and everybody can 
just use SMTP if they *NEED* this feature, but it would 
be 
nice, I think.