The default limit on the number of incoming messages that mayed by queued by your SMTP (Simple Mail Transfer Protocol) server is 100000 (One hundred thousand). When this limit is reached, no additional incoming messages are accepted by SMTP.

Using REG.EXE built into Windows XP and Windows Server 2003, or REG.EXE installed from the Windows 2000 Support Tools on the CD-ROM, I have scripted MaxSMTPQue.bat to set limit on the number of SMTP messages that may be queued.

The syntax for using MaxSMTPQue.bat is:

MaxSMTPQue NumbMsg ComputerName1 \[ComputerName2 ... ComputerNameN\]

Where NumbMsg is the limit you want to set, and each ComputerNameX is the NetBIOS name of a SMTP server you wish to configure.

MaxSMTPQue.bat contains:

@echo off
If \{%2\}
\{\} @echo Syntax: MaxSMTPQue NumbMsg ComputerName1 \[ComputerName2 ... ComputerNameN\]&goto :EOF
setlocal ENABLEDELAYEDEXPANSION
set wrk=%1
shift
set wrk=%wrk:"=%#
set wrk=%wrk:,=%
:lz
if "%wrk:~0,1%" NEQ "0" goto setNumb
set wrk=%wrk:~1%
goto lz
:setNumb
set wrk=%wrk:#=%
if "%wrk%" EQU "" @echo Syntax: MaxSMTPQue NumbMsg ComputerName1 \[ComputerName2 ... ComputerNameN\]&endlocal&goto :EOF
set /a NumbMsg=%wrk%
set /a CutOff=%NumbMsg% / 100
set /a CutOff=%CutOff% * 90
@echo.
:loop
if \{%1\}
\{\} endlocal&goto :EOF
set computer=%1
shift
set computer=%computer:"=%
set computer=%computer:\=%
@echo REG ADD "\\%computer%\HKLM\SOFTWARE\Microsoft\Exchange\MailMsg" /V MaxMessageObjects /T REG_DWORD /F /D %NumbMsg%
REG ADD "\\%computer%\HKLM\SOFTWARE\Microsoft\Exchange\MailMsg" /V MaxMessageObjects /T REG_DWORD /F /D %NumbMsg%
@echo.
@echo REG ADD "\\%computer%\HKLM\SOFTWARE\Microsoft\Exchange\MailMsg" /V MessageObjectsInboundCutoffCount /T REG_DWORD /F /D %CutOff%
REG ADD "\\%computer%\HKLM\SOFTWARE\Microsoft\Exchange\MailMsg" /V MessageObjectsInboundCutoffCount /T REG_DWORD /F /D %CutOff%
@echo.
goto loop