How to fix Exchange & Outlook connection issues over IPSec VPN


  1. cheers for taking the time to write this up as I “had” the same problem, and couldn’t find an answer.

    the only thing i did different was on the command

    set flow max-frag-pkt-size

    I used set flow max-frag-pkt-size 1500

  2. I’m having this issue – using site to site vpn Cisco ASA
    What to correct on the ASA. Is it the ASA for HQ or ASA atthe branch office? Thanks

  3. Hi, I’m having this issue too. I had change the tcpmss size on Cisco ASA (branch office) and PIX (HQ) change nothing. But the disconnects occured again.
    The only difference is, that i don´t get the error “MaxObjExceeded”, I get “MAPI session …exceeded the maximum of 32 objects of type “session””.

  4. For max sessions, look at the MS Exch RPC timeout setting on the Juniper

  5. I’m having intermittent disconnects and reconnects at our branch office between client outlook 2007 and exchange 2003. The client says trying to reconnect….it takes a random period of time before it reconnects to exchange. Exchange event viewer shows MAPI session…”cn=username exceeded the maximum number of 64 objects of type “session”” i changed the value from 32 to 64 but we are still experiencing the same problem.

    i’m starting to think it has to do with the VPN connection as stated above. We have a ASA 5505 at our branch office.



  6. Thanks for this article.. we had the same problem

  7. I have exactly same problem. The Outlook clients would connect OK but suddenly loose connection to the Exchange server and never connect back. I still can access shared folder of the outlook exchange server.

    This happens to me after I have launched VPN ip sec system. Previously I used leased line and had never have any trouble.

    When the outlook loose the connections I have to restart Exchange server every time to get it going. but not so long the problem occurs again and that’s nightmare.

    I have read this article and it is really big hope for me but..
    my system doesn’t have any firewall device. the only firewall found is on the cisco RV042 router but there is no MSS setting. there is only MTU setting.

    How can I fix this issue.

    Please help.

  8. we had the same issue with our branch office connected via SSG-5 to the headquarter. Changing the values above did not help, but after deactivating the “Microsoft RPC” ALG, the problem went away. Another possibility would be to increase the service timeouts for exchange.

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