thanks len always a great help
----- Original Message ----- From: "Len Conrad" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, October 11, 2003 8:58 PM Subject: Re: [IMail Forum] PTR record for a virtual IP > > >Let me rephrase my question > >when a user on a virtual domain domain2.com send an email via the server > >host domain1.com, will smtp identify itself as Domain1.com or Domain2.com? > > I looked up this "Imail helo's as" in the u/g and kb, and couldn't find for > sure (esp since it's an important point), but I think I remember an answer > in this list from Ipswitch person that Imail helo's with the > default/canonical hostname for a given IP. > > >does the answer depends on whether the user authenticated or not ? > > I would say no. there's no correspondance. Imail SMTPD > greets+authenticates, but it's IMail SMTP that sends. Imail doesn't change > it's HELO hostame to match every outbound @sender.domain it sends. eg, > what about users who send through IMail using a domain that is not even an > Imail domain, real or virtual? > > >If the answer is Domain1.com, then the "from" [EMAIL PROTECTED], will be > >different from the ehlo/smtp/PTR > >Is that tested by some servers ? > > Sure. > > eg, to prevent common forgeries of the helo hostname using the domains of > BigISP (yahoo, hotmail, etc), IMGate can do this logic: > > if helo is /BigISP/, then PTR must be /BigISP/. > > if sender.domain is /big ISP/, then PTR must be /BigISP/ > > if PTR is /BigISP/, then sender.domain must be /BigISP/ > > etc, etc. > > >can it be a problem ? > > not in general. > > As I said, the ptr/helo/smtp-greet hostname is identified with the physical > machine and its IP address, independent of the (virtual) envelope > sender/recipient domains the machine emits/receives. > > There is no required correspondence between a domain's MX hostname and PTR > of IP it resolves to. > > somedomain.com MX 10 mx.whatever.com. > > but somedomain.com is not involved in matchup of: > > mx.whatever.com. A A.B.C.D > > D.C.B.A.in-addr.arpa PTR mx.whatever.com. > > And then the MTA at IP A.B.C.D : > > SMTP-greets as mx.whatever.com > > HELOs as mx.whatever.com > > > Len > > _____________________________________________________________________ > http://MenAndMice.com/DNS-training: Wash DC; Dallas; Atlanta > IMGate.MEIway.com: anti-spam gateway, effective on 1000's of sites, free > > > To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html > List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ > Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ > To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
