Hector Santos wrote: > in the same vain many SMTP receivers will fill in the missing 822 > required fields.
> FROM: <<-- x821.MailFrom
> To: <<-- x821.RcptTo
The latter should never be done. If there's a missing To: header,
an SMTP receiver should synthesize:
To: undisclosed-recipients;
Otherwise, you risk exposing Bcc: addresses.
(I suppose it's safe for the MDA to add a To: header upon final delivery
to one and only one recipient.)
Regards,
David.
