Re: Re Anonymous Final Destination and mail submission

> If you are "final destination" (ie: Are an SMTP Server acting as a MTA 
> due to being pointed to by a MX) you have to assume that the MTA that is 
> relaying the message to you for delivery has verified that Mail From so 
> you HAVE TO assume that it is valid/usable.
This is clearly not the case.  If the DNS name in the MAIL FROM address 
is invalid you can't send a bounce message to it anyway, so you don't 
"HAVE TO" use it.  In a world where a significant percentage of mails 
received have bogus MAIL FROMs and/or bogus RCPT TO addresses or are 
undeliverable for other reasons, checking the DNS name of the MAIL FROM 
_before_ you agree to relay mail to a recipient starts to make sense.