HTTP 400 Bad Request

We experienced a power failure at our main office which shut down our Exchange server.  After it was brought back up all our remote computers at two separate branch locations were unable to connect to the Exchange server using either Outlook Anywhere or OWA.  Outlook simply disconnects.  OWA generates the error "HTTP 400 Bad Request" after entering the login credentials.  Other remote computers outside the branch locations have no problem connecting to the Exchange server using either Outlook Anywhere or OWA.  Interestingly computers at the branch locations have no problem connecting to another Exchange server at a completely unrelated business location.  Exchange is working fine for all users at the main office.  The Exchange server is running Windows 8 and is current on all Windows updates.  Servers and desktops have been rebooted.  Routers have been restarted.  There are no errors in the Exchange server Event Viewer.  I am completely baffled as to why only the computers at each of the two branch locations are having problems.  Does anyone have any idea as to what might be causing this problem?
smoakinAsked:
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JohnBusiness Consultant (Owner)Commented:
You would have some sort of router / VPN connection connecting Branch to Home Office. The home office end of this would have failed in the power failure as well.

Do you have a configuration file that you can re-import into the VPN?  

... Thinkpads_User
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smoakinAuthor Commented:
We aren't using a VPN.  Just a router.  I thought it might be a corrupted routing table and rebooted all three routers.  Again, other computers can connect if they are not inside the branch networks.  And it's only with Outlook and OWA.  Computers inside the branch networks can connect using Remote Desktop to a Terminal Server at the main office.
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JohnBusiness Consultant (Owner)Commented:
Just a router.  I thought it might be a corrupted routing table

Thank you for the clarification. Even if just a router, I think the question is still valid.

Your Exchange Server seems OK. I assume by "reboot" you mean you got a clean shut down and start up of Exchange. Further it is working OK locally and otherwise.  Did you check the network configuration files of the Server?

Your branch site is working to other locations.

So then the thing left over is the main office routers.  Can you rebuild the configuration of the routers from backup configuration files?  Might one of the routers have been fried in some way?  That has happened before.  Is there any chance DNS could have changed with the shutdown and then power up of the routers?

... Thinkpads_User
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smoakinAuthor Commented:
I agree that everything points to the router.  The strange thing is that there is no problem with other computers outside the branches from connecting to the Exchange server.  Is it possible/probable for a router/firewall to malfunction and only block computers at two different IP addresses but permit all others to pass using the same protocols?
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JohnBusiness Consultant (Owner)Commented:
Your router must have some configuration to permit specific IP addresses, so it seems feasible that the power outage damaged the configuration.

... Thinkpads_User
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smoakinAuthor Commented:
I will check the router. If I don't find anything I'll replace it to determine if that resolves the problem.
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smoakinAuthor Commented:
Reconfiguration of the router resolved the problem.
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JohnBusiness Consultant (Owner)Commented:
@smoakin - Good news! Thanks for the update and I was happy to help.

... Thinkpads_User
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