troubleshooting Question

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

Avatar of David Borg
David Borg asked on
14 Comments1 Solution143 ViewsLast Modified:
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 Administrator

Our community of experts have been thoroughly vetted for their expertise and industry experience.

Join our community to see this answer!
Unlock 1 Answer and 14 Comments.
Start Free Trial
Learn from the best

Network and collaborate with thousands of CTOs, CISOs, and IT Pros rooting for you and your success.

Andrew Hancock - VMware vExpert
See if this solution works for you by signing up for a 7 day free trial.
Unlock 1 Answer and 14 Comments.
Try for 7 days

”The time we save is the biggest benefit of E-E to our team. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange.

-Mike Kapnisakis, Warner Bros