Connection to Microsoft Exchange has been lost. Outlook will restore the connection when possible

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I didn't have any connection problems until I injected 700MB pst file in to a users mailbox (cached mode)

So here is the scenario:

Server: Windows 2008 x64 with Exchange 2007 Enterprise (Virtual on ESXi Server)
Client Windows Ultimate x86 with Outlook 2007

As soon as I imported the PST file in to outlook I started getting

Event IDs 9646 on the server

Mapi session " /o=First Organization/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=tom" exceeded the maximum of 32 objects of type " session" .

Increasing the limit in the Registry to 512 didn't fix the connection problem, but took care of the event 9646 on the server.

Clearing Download shared folders (excludes mail folders) in outlook on the client pc didn't fix the problem.
Event id 26 gets logged on the client every 10 sec

Connection to Microsoft Exchange has been lost. Outlook will restore the connection when possible.


Connection to Microsoft Exchange has been restored.

Client is located at the remote location with a hardware VPN between locations

Symantec EndPoint Protection is installed on the client, but shutting it down does not make any difference.

This is not a network problem, as I can copy 300MB file from the client to the server and back without any problems.

Does anybody have any ideas?

AndyD_ [MVP]

Does it getter in online mode or if you delete the .ost associated with that outlook profile and let outlook recreate it?


I just open Outlook client, see it connect automatically to the server then Inbox starts its replication I see " Waiting to update Inbox" message at the bottom starts at 2.17Mb (Inbox Folder size) see it go down to 700Kb and then it disconnects then within 10 seconds it reconnects again starts the replication and fails.

It's kind of in a loop

Folder sizes show

Client (786Mb) Server (137Mb)

So the client has to push over 600Mb to the server


If i delete the OST i will lose emails because some of them have not been synced with exchange.

AndyD_ [MVP]

the .ost is just the cache of the mailbox. Why would you lose mail?

You still have the original pst yes?

( you can always create a new Outlook Profile with a different name as well and leave that profile as is - the .ost is associated with the profile)


something else to add.

Exchange is on the Network
Client is on the Network

Linksys RV082 is on the client side
Linksys RB042 is on the server side
Hardware VPN is established between the routers.

If I try to RDP from ANY client on the 11 network to a 2008 server on the 10 network RDP session terminates within 5 sec (don't remember the error message)
If I try to RDP from ANY client on the 11 network to a 2003 server on the 10 network RDP session will last forever (no problems)

If I forward 3389 to a 2008 server from outside, RDP will last forever. Even tested with a broadband card connected to the same client (laptop) that was on the 11 network.


Yeah I still have the original PST file. This does not look like a profile problem.

Here is what I am gonna try. I will create a new user on the server and login as that user on the client, configure outlook import my PST again.
I am 100% connection issue will start as soon as replication starts.


Inbox had some email in it before i imported the PST, so now it has a mix of old and current emails.


RDP failures had nothing to do with Outlook disconnects.RDP issue was caused by Large Send Offload disabled on the client but enabled on the server.

I am guessing settings have to match?


Got a wireshark trace from the Client.

Looking at the MAPI protocol I see a pattern.

Outlook was started 41 seconds in to the trace. At 45.4 sec I see a client's request for EcDoDisconnect, but no server response. 10 milliseconds later client send another EcDoDisconnect, still unanswered, third EcDoDisconnect goes out unanswered and finally at 47 sec client sends another EcDoDisconnect which gets answered in the next packet by the server.

I guess at this point MAPI session is torn down and the process starts again

Client sends 3 EcDoDisconnect requests at 48 seconds and 4<sup>th</sup> sent and 50 sec gets answered.

Ajaj Desai MCP


try to run these following commands on client using cmd

ipconfig /flushdns

and test the domain controller connectivity by using following command

dcdiag (support tools need to be downloaded)

Regards, Ajaj Desai (India)


Exchange is on the same box with DC.

Will run dcdiag, but not sure if this is a troubleshooting step in the right direction.

Novak Wu


Does the issue occur when importing the PST file to another Exchange user on another machine?

Based on my research, I found that there was a familiar issue in the following article and it was resolved successfully. I suggest you refer to the suggestions from the following article to troubleshoot the issue.
Hope this helps.Novak Wu


Router"s MTU didn't match, so there was an issue with fragmentation.
Since the issue was on the lower network level (transport), application errors were misleading.

Novak Wu


I would like to confirm whether the issue is resolved now. If not or there is any other problem, please feel free to let me know.


Novak Wu
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