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VPN user unable to use Cached Exchange Mode while on VPN

Shortly after a recent upgrade from a Sonicwall TZ 170 to a TZ 190 (w/latest firmware) I have 1 user who is unable to update his Outlook 2003 mailbox while using Cached Exchange Mode to the Exchange Server 2003 SP2 server over the VPN.

I dd receive a single instance of event ID 9646 for exceeding the maximum of 32 objects of type "session"  for this user. I proceeded to increase the maximum on the server to 64 without any change.  

If I turn off the cached mode, Outlook works fine, but has the typical delays associated with not using Cached mode.

For whatever reason, when I do a send/receive command it says it works fine, but the in the lower right corner the mailbox indicates is was last updated 2 days ago and none of the current mail shows with the  cached mode on.

FYI - The user in question has a 2.8GB mailbox....all the other users are 1GB or less, but it worked fine until recently.


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8/22/2022 - Mon

We encountered this problem as well with a client, although it wasn't related to VPN or SonicWALL appliances (they also use both, but with a Pro 1260).  We wound up having to restart the Exchange 2003 Services to clear out all of the cached connections on the server.  This client machine that has this issue has a number of Outlook Add-ins that we believe is causing the additional "hanging" connections (that remain after Outlook is shutdown by that user).

I hope this helps or gives you some ideas...

sounds like a corruption to the cache or even the mailbox its self...

You may want to delete the cache and rebuild it while on the LAN then try remote sync again.

Otherwise, check the exchange mailbox and do some maintenance on the server to check it's kosher.
essutil etc..

Poor VPN connections can play havoc with large exchange clients, time for a cleanup too...

Thanks for the quick replies and here is some additional info:

1. We have already restarted the server to clear the connections....no help.
2. The computer in question is a home workstation not a laptop...so it is never on the LAN. There is another desktop on the LAN the user uses without issue.
3. VPN connection appears pretty rock solid. High speed connections both sides and virtually no packet losses.

Thanks again.
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then what about trying to repair the cache file itself, using ostscan ? Does that help?

In Outlook, disable Exchange Cache Mode.  Close Outlook.  Locate the OST file (such as within %APPDATA%\Local Settings\Microsoft\Outlook.  Re-load Outlook and setup Exchange Cache Mode.  Check to see if it starts synchronizing with Exchange (you may need to restart Outlook).

What do you want me to do with the OST file after I find it?
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you can use C:\Program Files\Common Files\System\MSMAPI\1033\SCANOST.EXE
to check its integrity.

OKay, so I tried Arkware's advice and disabled the cache and reconfigured caching with a new . OST file. It almost immediately began to rebuild over the VPN. After several hours the VPN connection was lost. I reset the VPN connection and the rebuild continued. (2.8 GB rebuild takes awhile). It got to just over 2 GB and died. A scanost.exe will not complete (errors out). As I recall, new Unicode format for the .OST does not have a 2GB size limit so it could be a random that stopped at just over 2GB. Thoughts

FYI - The rebuild died not the VPN connection. That was fine.
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