> Sorry for the confusion.

No problem...but you're still a bit confused. :)

> The situation is I have two different hosts that are responsible for the
> domain.com.

Okay,  let's  stop  right  there. As I tried to describe earlier, if a
host  performs  local  delivery  to  a domain, this means that, unless
specifically told otherwise, it will consider an address @ that domain
to   be  nonexistent  (and  generate  a  5xx  error  during  the  SMTP
transaction)  unless  it  is  found in its directory of users for that
domain.

Conversely, if a host performs remote delivery (relaying) to a domain,
this  means that, unless specifically told otherwise, it will consider
an address @ that domain to be deliverable to any one of the other MXs
for that domain, but NOT to itself.

Without  realizing  it, you are looking for your hosts to consider the
same  domain  to  be  both local and remote, depending on the username
(the  'local-part') of the recipient address. Make sure you understand
this  concept  before continuing, and realize that making your systems
perform  in  this way is non-traditional, and may not be easy, or even
possible, depending on the software platforms in use.

You  are  probably  wondering  by  now,  "Well, then what the h*** are
primary  and secondary MXs for? Aren't they a traditional use of SMTP,
and don't they do this by definition?" The answer is no: no matter the
number  of  MX  records,  in  traditional  SMTP, the *final* recipient
domain usually has only one mailbox server (server that performs local
delivery  to  mailboxes). "You mean every address @hugeisp.net ends up
on  the same POP3 server?" you ask. Again, no: through the use of that
manage  routing and aliasing, [EMAIL PROTECTED] can be routed straight
through   to   the   mailbox   server   for  hugeisp.net  without  any
modification,   while   [EMAIL PROTECTED]  can  be  translated  before
delivery into [EMAIL PROTECTED] and routed to the mailbox server
for  mail2.hugeisp.net, [EMAIL PROTECTED] can be translated in transit
into  [EMAIL PROTECTED],  and  so  forth.  You  are  essentially
implementing  a  variation  of  this whenever you give a mobile user a
local alias for their (AOL) address, without a local mailbox.

But  back  to your setup. You are trying to extend IMail beyond SMTP's
basic local delivery vs. remote delivery decision, trying to partition
a  single  domain across local and remote mailboxes. You could do this
in  a  user-by-user  way,  by  making  sure  that imail.domain.com and
exchange.domain.com  are  the MXs for their respective hostnames, then
creating   user   aliases   on   the   IMail   server  that  translate
[EMAIL PROTECTED] into [EMAIL PROTECTED] But Ipswitch also has
a very cool peering function (read up on it, like I suggested) that is
able,  in  essence,  to  automatically look for any domain.com address
that  it  doesn't  have a local mailbox for on another server that you
designate  by  IP address. So with peering in place, you wouldn't have
to  manage  any non-local aliases on the IMail side--just leave people
out  of  the local database and they'll automatically looked up on the
remote  server  (you do have to make a one-time change to the Exchange
SMTP greeting, but that is a drop in the bucket).

Yet  there's  always  a catch when you're not only stretching SMTP but
mixing  platforms,  too.  IMail  peering  is  great, but it only works
bidirectionally  between  IMail servers; Exchange has no such wildcard
function  to  go  back  in  the  other  direction (things are somewhat
different  if  you  are using an all-Exchange network, as you can have
transparently  distributed  mailbox  servers).  So if someone tries to
send  to a non-Exchange user through the Exchange box, unless Exchange
has  the  non-local address [EMAIL PROTECTED] (or, in AD, the Full Name
of the user) aliased to [EMAIL PROTECTED], the mail will fail, as
it does now.

> Sounds  like I need something in the wins hosts file to detail their
> existence to each other.

Not  WINS (LMHOSTS), I suppose you mean, but HOSTS. But no, that won't
help either.

Make sense now?

-Sandy


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