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Reverse Resolution

You can disable reverse resolution lookup for SMTP mail sent to the Internet Mail Service. Reverse resolution is when the name of the host that delivered an incoming SMTP message is resolved and placed into the message header by the Internet Mail Service.

When an SMTP message is received, the host address is contained in the message header. The header describes the path of the message as it traveled from the host that sent the message to the host that received the message. The following is a sample SMTP message header with return path and time stamps.

Received: from GHI.COM by JKL.COM ; 27 Oct 96 15:27:39 PST
Received: from DEF.COM by GHI.COM ; 27 Oct 96 15:15:13 PST
Received: from ABC.COM by DEF.COM ; 27 Oct 96 15:01:59 PST
Date: 27 Oct 96 15:01:01 PST
From: JOE@ABC.COM
Subject: Upgraded Mail System
To: SAM@JKL.COM

Disabling Reverse Resolution

You can increase Internet Mail Service performance by disabling reverse resolution. When reverse resolution is disabled, the Internet Mail Service will not resolve the host name in the upper most Received From portion of the SMTP message header. If the address is in Internet Protocol (IP) form, the address will remain as such.

  1. Open Regedit.exe or Regedt32.exe.
  2. Open the following registry keys:
    3. 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 DisableReverseResolve; under Value data, type 1. If you are using Regedt32.exe, type DisableReverseResolve; under Data Type, choose REG_DWORD.
  5. If you are using Regedt32.exe, under Data, type 1.