Speaking of which, by mere coinkydink I needed that article right now 
too. Yet my ISPs SMTP server doesn't seem to let me through; does anyone 
know what are the common limitations that ISPs enforce on e-mails sent 
via their SMTP servers? I'm wondering whether setting my HELO domain to 
my webhost's as opposed to something that looks like what the ISP might 
have given me could cause a failure in the mail being deliverred.

More generally, is there any way to check on the status of a mail sent 
via SMTP?

David Vallner