Route email for unresolved recipients to external Exchange server

[David Hartry]

Hi,

I've posted this on the SBS group but had no response, since it's completely
to do with Exchange hopefully someone in here will be able to help...

One of our clients is actually 2 sister companies, each with their own
office, geographically dispersed. One has a SBS2000, the other SBS2003.
Each has their own email domain and both servers receive email for their own
domain through SMTP.

In reality the two companies are very tightly interwoven, to the degree that
users in company 1 need not only their company 1 email address
(us...@co1domain.co.uk) but also the corresponding email address in company
2's domain (i.e. us...@co2domain.co.uk)

So, I have added co2domain.co.uk to the recipient policy on company 1's SBS
(this one is 2003) and vice versa on the other server. I unchecked the
'responsible for all mail delivery to this domain' option at both servers.
Initially I thought I would need to uncheck this option for the other domain
at each end as well, but it's greyed out so obviously not.

Next I went to the default SMTP virtual server properties, messages, and set
the 'Forward all mail with unresolved resipients to host' option to the
internet FQDN of the SBS in the other company. Obviously I did this at both
ends.

I hope this has made sense so far.
OK, so I thought that was all I needed to do. I set up a test user at
company1 with email addresses for both domains. But if I send mail to the
company2 domain address, it doesn't arrive.

AFAIK the process would be: the originating (my) SMTP server looks up the MX
for domain2, finds it at company 2's SBS, and sends the message there. The
SBS at company2 sees that it can't resolve the recipient locally, so it
forwards it to company1's SBS as I have specified. SBS at Company 1 is set
up through the recipient policy to also accept mail for the company2 domain,
so it does so and sees the email address belongs to the test user I set up,
so puts the email in his mailbox.

But it doesn't.

Furthermore, I just received the following NDR:

Your message did not reach some or all of the intended recipients.

Subject: test to company2.co.uk
Sent: 25/8/2005 9:44 PM

The following recipient(s) could not be reached:

test...@company2.co.uk on 25/8/2005 11:03 PM
A configuration error in the e-mail system caused the message to
bounce between two servers or to be forwarded between two recipients.
Contact your administrator.
<sbs.comany2.co.uk #4.4.6>

Looking at my prvious description of the process, it would seem to me that
the email is getting to SBS at company2, and this server forward it to SBS at
company1, but this SBS sends it back as an unresolved address to SBS at co. 2
(hence causing the loop). Am I right? Why won't co.1 SBS see this email as
resolvable?

What have I done wrong/omitted?

Thanks in advance

--
Regards,
David Hartry
--

[Mark Arnold [MVP]]

To be honest, in your case I'd follow:
http://support.microsoft.com/kb/321721/en-us/ to interoperate the two
domains and using Recipient Policies to give each user both addresses
(as you have done and know)

I know where you're coming from with the forwarding and you clearly
know what you're about, but I think the sharing of the address space
might be the better route. It will prevent the bounces you've been
suffering.

[David Hartry]

Thanks Mark, and thanks for the respect, I don't consider myself to know much
about exchange (I've never done an Exchange exam) so that made my day!

The KB seems pretty straight forward, I can't see any SBS specific problems
at first glance, so I will give it a go and post back if I have any more
issues.

Thanks again

--
Regards,
David Hartry
MCSE
--

[David Hartry]

Hi Mark,

OK I've followed the instructions in the KB but still no joy. Basically I
now have two domain namespaces shared over two servers. But neither of them
will succesfully forward to the other server.

I have followed method one in the KB to the tee: added an internal
authoratitive email domain to each server & set as primary, unchecked the
authoritative option for the internet domain on each server, and created a
new recipient policy with highest priority to set the users' email addresses
to the internet domain (although I don't think this has any bearing on the
problem I'm experiencing).

Then created 2 new SMTP connectors (one at each server), set the 'forward
all mail to smart host:' option to FQDN of other server, set the bridgehead
to the default SMTP virtual server, and (the only bit I wasn't 100% about)
set the SMTP address on the Address Space tab to *the domain for which this
server is authoratitive* (although it isnt any more!) - this sentence doesn't
make sense but do you see what I mean? In other words I set the SMTP address
on name space tab to be that of the recipient on the emails that will be sent
across it to the other server. Also checked the 'allow messages to be
relayed' option.

Now when I send emails that *should* go across the new SMTP connectors, I
receive a different NDR depending on which server:

SBS 2000 gives:

Your message did not reach some or all of the intended recipients.

Subject: test
Sent: 26/8/2005 10:00 PM

The following recipient(s) could not be reached:

te...@company1.co.uk on 26/8/2005 10:14 PM
You do not have permission to send to this recipient. For
assistance, contact your system administrator.
<sbs.company1.co.uk #5.7.1 smtp;550 5.7.1
<te...@company1.co.uk>... Relaying denied>

and SBS2003:

Your message did not reach some or all of the intended recipients.

Subject: test
Sent: 26/8/2005 10:00 PM

The following recipient(s) could not be reached:

te...@company2.co.uk on 26/8/2005 10:02 PM
There was a SMTP communication problem with the recipient's
email server. Please contact your system administrator.
<company2.co.uk #5.5.0 smtp;553 sorry, that domain isn't in my
list of allowed rcpthosts (#5.7.1)>

I'm guessing the different NDRs are due to different default permissions in
EX 2K/2003??

Any ideas anybody/Mark?

Thanks

--
Regards,
David Hartry
MCSE
--

[c King@discussions.microsoft.com Martin c King]

Just a thought perhaps you need to allow your ips to relay through the server.