SYMPTOMS
When the number of concurrent inbound SMTP connections reaches 2,000, users may not be able to connect to your server, and they may receive the following error message:
Error on telnet port 25:
421-Microsoft ESMTP MAIL Service, Version: 5.0.2195.6713 ready at Service not available,
closing transmission channel
Connection to host lost.
RESOLUTION
Hotfix information
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that are experiencing this specific problem.
To resolve this problem, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:
Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.
Prerequisites
Windows 2000 Service Pack 4 (SP4).
Restart requirement
You must restart your computer after you apply this hotfix.
Hotfix replacement information
This hotfix does not replace any other hotfixes.
File information
The English version of this hotfix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the
Time Zone tab in the Date and Time tool in Control Panel.
Date Time Version Size File name
----------------------------------------------------------
13-Nov-2003 21:34 5.0.2195.6872 322,320 Aqueue.dll
13-Nov-2003 21:34 5.0.2195.6824 67,856 Mailmsg.dll
13-Nov-2003 21:34 5.0.2195.6872 38,672 Ntfsdrv.dll
13-Nov-2003 21:34 5.0.2195.6874 445,200 Smtpsvc.dll