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 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'. No wonder some call 'BT' Balls-up Telecoms. Do your Mail Transfer Agents use valid or bogus HELO/EHLO names ? -- With best regards, Paul. England, EU.