PC Win: Mail Fails on Wollongong TCP/IP and LAN Manager 2.2

• Microsoft Mail for Windows, versions 3.0 and 3.2

SYMPTOMS

When you use Wollongong TCP/IP with Microsoft LAN Manager version 2.2, the Mail Windows client may fail when you access the Mail message file. Error conditions include:

• Mail cannot send or receive messages because of problems downloading a message.
• Microsoft Mail caused segment load failure in module USER.EXE.
• An unexpected memory or network error occurred. Computer informed user that changes may have been lost and to quit mail and restart.
• Mail is unable to save information to message file.
• Folder could not be accessed.
• Error occurred while views were being saved. Some views may not be restored at start up next time.
• Some information could not be written to disk. Changes may have been lost.

CAUSE

This problem is caused by Wollongong's TCP, which does not support the full command set of Microsoft TCP. When a session is broken, Wollongong TCP does not inform the workstation, causing Mail to exhibit the behavior above.

When you run LAN Manager version 2.2, the opportunistic locking function (called Oplocks and designed to enhance performance by caching server data on the workstation) disconnects Mail's session. Mail normally opens the Mail message file twice (for STORE.DLL and MSSFS.DLL). When one of the DLLs writes to the Mail message file, the server issues an Oplock Broken command that is supposed to inform all users of the file to flush their buffers and re-read the server file. This is to ensure that the cached data on the workstation is current. If the re-read operation does not occur within a time-out period (definable in the server heuristics) then the connection is broken by the server to ensure the data on the workstation is valid. When this happens to Mail, one of the two DLLs (the one that hasn't written to the Mail message file yet) still attempts to use the (now invalid) session. The DLL fails and one of the error conditions above occurs.

RESOLUTION

Do one of the following to eliminate the problems:

• Substitute Microsoft TCP/IP for Wollongong TCP/IP.
• Move the Mail message file to a local storage location.
• Turn the server's Oplock function off. See the LAN Manager Administrator's Reference for the specific heuristic value.