Re: [vps-mail] Multiple domain on VPS - rDNS for mail doesn't match mail server

[Harrison Hind <hhind@xxxxxxxxxxxxx>]

On Thu, Jan 22, 2004 at 04:35:05PM +0100, Marjolein Katsma wrote:
> The server actually services three domains; main domain javawoman.com, with 
> two more, all serviced by the
> same email server (sendmail) at the same IP address (additional domains set 
> up as virtual domains in sendmail config).
> 
> Is there some way I can adapt the sendmail configuration so that for each 
> of the domains it reports the correct mail server host name? Or something 
> else I can do to correct this?

  No.
  Understanding how the protocol works behind the scenes helps to explain 
why.  There is a definite format to the conversation -- sort of like a 
scripted telephone call.  When a mail program runs, it listens for 
connections on a specified ip/port  (comparable to your phone number).  When 
it receives a connection, it has access only to the ip from which it 
comes (sort of like caller-id)  The first thing the smtp protocol requires is 
that the answering server announces who it is.  (Hello, this is the Hind 
residence).  At this point you have no idea who the email is for, or who is 
actually sending it. It is only later in the conversation that the sender and 
recipient (including recipient domain) are identified.  So how can you know 
what name to use when you answer.  (Now admittedly, when I answer the phone, 
and the caller-id shows that it is one of my wife's friends, I sometimes 
answer with "Hello, this is Callie's house") But I don't think that sendmail 
is configurable to answer differently based on incoming IPs, and furthermore 
it wouldn't be very practical...


Harrison.

PS btw, this is the same reason why certificates have problems with virtually 
hosted domains in https.
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