On Thu, 18 Jun 2015 11:36:01 Bill Cole wrote: > On 17 Jun 2015, at 3:00, Michael Peter wrote: > > Hi, > > > > I understand that postfix send bounces or failed delivered > > notifications > > using empty sender. > > As does every MTA which in compliance with the SMTP standards of the > past >25 years. > > See https://tools.ietf.org/html/rfc5321 and its linked ancestors for > details. > > > But does postfix accept empty sender emails during the MAIL FROM > > command > > during the SMTP conversation? > > Yes, unless it is misconfigured to reject the null (empty) sender. > > > because i think that postfix needs a valid > > email address ? > > No, it needs a valid SMTP return path value, which can either be an > email address OR null. > > > if postfix reject empty sender emails during receiving of emails, so > > how > > come bounces and failed delivered notices are received from other > > email > > servers ? > > The condition of your 'if' clause is not normally met. > > > The reason i am asking for that in order to block some spam attacks on > > our > > email mail server that using empty email senders > > Do not block mail simply because of a null sender, as that will > eliminate all valid email failure notices generated elsewhere. Find > another way.
If you're able to sign all your outgoing email using BATV envelope senders you could reject all messages with an empty/null sender that wasn't to a correctly signed BATV recipient at your MX. The only limitations here is that you can't guarantee BATV signed email on a domain which runs mailing lists or other applications that encode information in the envelope sender.
