Member Avatar for gavm99

Hi all,

I will try to keep this as simple as possible.

I have a customer who has a Sony Vaio Laptop at home, along with a Netgear Router which he connects to using Wireless and the ISP is AOL. He uses a PPTP VPN

connection to connect to the office and then uses Outlook 2003 to check his emails.

The problem is that whenever he trys to reply or forward an email Outlook either crashes or simply doesn't do it.

What ISN'T the problem here:

1) It is not the VPN. The VPN is stable and there is no packet loss when pinging the server. The VPN also works fine on the same machine when using a 3G

connection.

2) It is not the ISP. My laptop connecting to his router works fine.

3) It is not the router. My laptop connecting to his router works fine.

4) It is not the installation of Office because it all works fine over 3G and when he is in the office.

5) It is not a DNS issue as there are entries in the hosts file and again all works fine via 3G.

6) It is not a WLAN issue only as the same occurs when using the LAN connection with a network lead. The latest device drivers have been installed.

My thoughts are that it is something to do with the way the WLAN and LAN adapaters on his laptop handle the VPN and Outlook traffic but I am really out of

ideas.

I am open to any suggestions!!!

Many thanks in advance.

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  • Latest Post Latest Post by zelkea

Dani AI

Generated

Short diagnosis tied to the thread: given the behaviour described (single Vaio only misbehaves when on the home link + PPTP but works over 3G and in-office, and another laptop on the same router is fine) the fault is very likely local to that laptop’s network stack/filter drivers or an MTU/packet-offload interaction with the PPTP tunnel — not Exchange itself. ’s idea to test SMTP is useful when the account is SMTP/POP, but an Exchange/MAPI client needs different checks (RPC endpoints, Winsock/LSPs, NIC offloads, etc.).

Recommended troubleshooting steps (in order):

  • Rule out Outlook add-ins and profile: run Outlook in safe mode:

    outlook.exe /safe

    and try composing/replying. Also test with a fresh Outlook profile.

  • Eliminate local filters: temporarily disable antivirus e-mail scanning and any third-party firewall/VPN/filter drivers. Check Event Viewer after a crash for a faulting module name (that DLL often identifies the culprit).

  • Reset the Windows TCP/IP stack and name caches:

    netsh winsock reset
netsh int ip reset
ipconfig /flushdns

    Reboot and retest.

  • Check NIC offloads and MTU: disable Large Send Offload / Checksum Offload in the adapter Advanced properties. Test MTU with:

    ping -f -l 1472 <server-or-vpn-gateway-ip>

    Reduce the payload until replies succeed; MTU = payload + 28. If fragmentation is the issue, set a lower MTU/MSS on the client or clamp MSS on the router.

  • Targeted diagnostics: enable Outlook logging (Options -> Other -> Advanced -> logging) to capture RPC/HTTP errors; use a short packet capture (Wireshark) to look for TCP resets/GRE fragmentation; for Exchange test RPC endpoint reachability (PortQry or similar); for SMTP/POP accounts test with telnet or a small mail client as suggested.

Caution: back up settings before registry edits or persistent driver changes. If none of the above isolates the fault, the crash trace / Event Viewer entry or a short packet capture will usually point to a specific add-in or network filter driver to remove.

Member Avatar for zelkea

Gavm99,
Have you tried using another application to test connectivity over port 25? While troubleshooting a SMTP problem I was having I found this little 20K application called “quick mailer” that helped me troubleshoot my problem. I would be interested to see if you able to successfully send an email using this app, btw it is free.

AJZ

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