DOCUMENT:Q131422  28-OCT-1999  [pcmail]
TITLE   :PC Ext: Purpose and Function of -V20 Switch
PRODUCT :Microsoft Mail For PC Networks
PROD/VER:WINDOWS:2.1,3.0,3.2
OPER/SYS:
KEYWORDS:

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The information in this article applies to:

 - Microsoft Mail for PC Networks, versions 2.1, 3.0, 3.2 
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SUMMARY
=======

This article describes the purpose and function of the -V20 or CompatV20 switch
used with the EXTERNAL.EXE program for versions 2.1, 3.0, and 3.2 of Microsoft
Mail for PC Networks.

MORE INFORMATION
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To remain compatible with Microsoft Mail version 2.0 and related gateway
programs, Microsoft Mail for PC Networks, versions 2.1 and later requires the
use of the -V20 (CompatV20 in EXTERNAL.INI file) command-line option. Current
versions of Microsoft Mail for PC Networks (versions 2.1 and later) are still
compatible with the previous Microsoft product (version 2.0). This compatibility
means that version 2.0 of Microsoft Mail should be able to transfer mail to a
later version of Microsoft Mail using the latest version of the Microsoft Mail
Message Transfer Agent (MTA), EXTERNAL.EXE.

To remain compatible with version 2.0 Mail and related gateway programs,
Microsoft Mail for PC Networks versions 2.1 and later allow the use of the -V20
command line option (or CompatV20 in the EXTERNAL.INI file). This option allows
the later versions of the External program to use the same type of file
creation, detection, and deletion algorithms that the version 2.0 used.

One function of External is to deliver mail to individual mailbags on a given
mail server. In order to do this, there has to be some mechanism by which
External keeps a mailbag open to put data into it. The MTAs that shipped with
version 2.0 of Microsoft Mail used a different mechanism to "lock" mailbags than
later versions use. This mechanism relied on file creation, detection, and
deletion to prevent "mailbag contention" (more than one process trying to access
the same mailbag at a time). Microsoft Mail for PC Networks versions 2.1 and
later rely on the file locking capabilities provided by the specific network
operating system to accomplish this task.

Therefore, because of the way in which the version 2.0 EXTERNAL.EXE locked files,
using the -V20 switch generally means that EXTERNAL.EXE will exhibit performance
degradation and be more input/output intensive. Because of this, Microsoft
discourages the use of the -V20 switch unless a version 2.0 postoffice or
gateway is involved.

If the -V20 switch is used for compatibility with version 2.0 postoffices or
gateways, it MUST also be used on all other MTA processes that interact with
them. For example, if the -V20 switch is used in a local area network, it will
probably be needed on all the EXTERNAL.EXE processes.

Notes:

 - Whenever possible, run the latest release of EXTERNAL.EXE or any gateway
   software for Microsoft Mail for PC Networks.

 - Version 2.0 of the Microsoft Mail for PC Networks products require the -V20
   switch, versions 2.1 and later do not require it.

 - For FFAPI-based gateways, check the version of the FFAPI component by typing
   the following command:

   " FFAPI_program -ver " (without the quotation marks)

   For example,

   " P:\MAILEXE\GTWGET -VER " (without the quotation marks)

Additional query words:

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Keywords          :  
Technology        : kbMailSearch kbZNotKeyword3 kbMailPCN320 kbMailPCN300 kbMailPCN210
Version           : WINDOWS:2.1,3.0,3.2

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