Cannot log into legacy Exchange 2007 mailbox in Coexistence via Outlook 2013 with Outlook Anywhere

I attempted to go into coexistence this last weekend but had to roll back due to not being able to connect to Exchange with Outlook 2013 externally. Everything else worked without a problem and Outlook would connect internally without a problem. OWA was able to proxy externally to the 2007 mailboxes without a problem.

I verified that the authentication setting were the same on both RPC vDirs (Exchange 20007 and 2013). I tried both Basic and NTLM for the ExternalClientAuthenticationMethod property (Basic would prompt for creds and NTLM would just not connect). IISAuthenticationMethods is set to Basic, NTLM.

Any ideas?

Server 2008 R2 level
Exchange 2013 and 2007 are in different sites
Same Forest/Domain

Exchange 2007:
2 Server 2008 R2 Exchange 2007 standard servers
Only one is configured with mailboxes, connectors, etc
No NLB as only one server is active and functional
IPv6 disabled via registry

Exchange 2013:
2 Server 2012 Exchange 2013 Standard Servers (non R2 Windows)
Microsoft IIS ARR 3.0 on server 2012 acting as proxy for primary mail namespace (
Autodiscover is set to use for resolution with corresponding scp records internally
IPv6 enabled
David BorgNetwork AdministratorAsked:
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Scott CSenior EngineerCommented:
Try doing a fiddler trace while you are reproducing the issue.

Make sure the HTTP traffic is unencrypted.  See if you can tell where the authentication prompts are happening.

Unfortunately Outlook logging can only be used if Microsoft is involved as the .ETL logging files created can only be viewed by them with internal tools.
David BorgNetwork AdministratorAuthor Commented:
I will have to try this when I can put us back into Coex.
Will SzymkowskiSenior Solution ArchitectCommented:
For Exchange 2013 you need to make sure that you properly NAT-ed to the 2013 CAS server on your firewall. Once you have done this then your Exchange 2013 clients should be able to access OWA without and issue.

Exchange 2007 clients will be re-directed automatically when they login to the Exchange 2013 OWA login page.

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David BorgNetwork AdministratorAuthor Commented:
OWA works fine and the proxy happens as it should. The problem is with Outlook Anywhere connections being proxied back.
Will SzymkowskiSenior Solution ArchitectCommented:
Outlook Anywhere should only be confiugred on the Exchange 2013 server. Did you have it confiugred in both places?

I would also suggest that you try using with an account on Exchange 2013.


Run through the Exchange Deployment Assistant to make sure that all of the steps have been completed correctly.

Exchange Deployment Assistant

AmitIT ArchitectCommented:
Please test with this site:

Select Outlook connectivity test and share the result.
David BorgNetwork AdministratorAuthor Commented:
It was configured on both servers as far as I could tell. I used the deployment assistant for the settings (checked and set 3 different times to make sure). I also make sure that the authentication in both locations matched precisely and the externalURL was set to

I did not use the connectivity analyzer (dumb mistake at 3am).
David BorgNetwork AdministratorAuthor Commented:
I will try to run the connectivity analyzer tonight and see what the results are. I will update accordingly.
David BorgNetwork AdministratorAuthor Commented:
Alright...I was able to run the connectivity analyzer last night but not fiddler (connection was flaky and I had limited time).

There was an error "Attempting to ping RPC proxy". It said the remote server returned error (404) Not Found. I attempted the test with a 2013 and 2007 mailbox.

When I received this error, I attempted to browse to and once logged in I received the blank web page but not a 404 error.

After doing a little research this morning, I may not have used the tool correctly. I selected to run the "Outlook Anywhere" test and entered all of the info. It is my understanding that the RPC Proxy Server name and the Exchange Server name are one in the same with Exchange 2013, correct?

Any ideas?
Will SzymkowskiSenior Solution ArchitectCommented:
depending on what test you are running you need to ensure that your autodiscover and is correct as well. How is your current Exchange certificate configured? What DNS names do you have on your UCC cert? Do you have autodiscover setup as an SRV record on your external DNS?

David BorgNetwork AdministratorAuthor Commented:
We do not have autodiscover set up externally. I entered the info manually.

The certificate is set to be used by all services and has these names (in this order):

*knucklehead moment*...I did find out that the firewall was enabled on the ARR server and could not ping the IIS ARR proxy server that goes through. I am disabling the firewall for now (we have to have them enabled for audit purposes) to test and will update accordingly.
Will SzymkowskiSenior Solution ArchitectCommented:
That is part of the NAT-ing that needs to be done for the Exchange 2013 server as i stated in my eariler post.

If it errors out again please post the exact error message.

David BorgNetwork AdministratorAuthor Commented:
I now have it working...the solution was to update the Maximum Allowed Content Length on the IIS ARR server to be 2147483648 (see below). Once this was done, it started working. Thank  you for all of the input.

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David BorgNetwork AdministratorAuthor Commented:
The solution was due to me missing that step.
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