Disabling ETRN Support

Microsoft Exchange Server supports the use of an SMTP extension called ETRN for dial-up connections using RAS. After the client host submits the ETRN command to the server host, a new connection is established from the server host to the client host, and mail to the client host domain is retried immediately.

You can disable ETRN using the Windows NT registry.

1. Open Regedit.exe or Regedt32.exe.
2. Open the following registry keys:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\
MSExchangeIMC\Parameters
3. If you are using Regedit.exe, choose Edit, and then choose New DWORD Value. If you are using Regedt32.exe, choose Edit, and then choose Add Value.
4. If you are using Regedit.exe, type DisableETRN; under Value data, type 1. If you are using Regedt32.exe, type DisableETRN; under Data Type, choose REG_DWORD.
5. If you are using Regedt32.exe, under Data, type 1.

For more information about using ETRN, see Microsoft Exchange Server Concepts and Planning, and RFC 1985, "SMTP Service Extension for Remote Message Queue Starting."