Am 17.07.2011 23:24, schrieb Always Learning: > > On Sun, 2011-07-17 at 23:15 +0200, Alexander Dalloz wrote: > > >> The 2nd one in your list: >> >> Organisation: British Telecommunications, EU >> HELO / EHLO: smtpe1.intersmtp.com >> HELO IP: 62.239.224.89 >> MX IP: 62.239.224.234 >> MX DNS A record: smtp61.intersmtp.com >> >> Here smtpe1.intersmtp.com resolves properly forward and reverse, if that >> is what counts for you. > > BUT the IP address used for the mail server was, as the list shows, > 62.239.224.234 which, at the time, had a host name of > smtp61.intersmtp.com What do you mean by that? Was the connecting mailserver the one with IP 62.239.224.234? If you mean that the mailserver should have been the one listed as MX, you are simply wrong and you do not know what an MX is. > smtpe1.intersmtp.com still does NOT properly resolve. > > host smtpe1.intersmtp.com > smtpe1.intersmtp.com has address 62.239.224.89 > > host 62.239.224.89 > 89.224.239.62.in-addr.arpa domain name pointer smtpe1.intersmtp.COM. > > *almost* correct. In Linux, like Unix and the pre-Microsoft days, > uppercase letters have a different numerical value to lowercase letters. > > Uppercase 'COM' is definitely not the same as lowercase 'com'. In DNS as well in mail addresses in the public zone the letter case does not matter. > No wonder some call 'BT' Balls-up Telecoms. > > Do your Mail Transfer Agents use valid or bogus HELO/EHLO names ? No, though there is no RFC which states that the HELO/EHLO name must be eqal to any MX record. In your example the greeting name resolves fine and is ok in this regard. Someone who does not want to receive mail from legitimate senders can just switch off his MTA ;-) Alexander