User Name Resolution

When the Internet Mail Service receives an SMTP message, it attempts to resolve the user name in the header against the Microsoft Exchange Server global address list. A user name is the name associated with an SMTP address. If the user exists in the global address list, the SMTP address associated with the user is replaced by the display name for the user's account. Otherwise, the name displays as the SMTP address.

Disabling User Name Resolution

When an SMTP message is received, the Internet Mail Service attempts to resolve the user name in the To, From, and Cc fields from the SMTP addresses. You can increase the performance of the Internet Mail Service by disabling user name resolution.

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 ResolveP2; under Value data, type 0. If you are using Regedt32.exe, type ResolveP2; under Data Type, choose REG_DWORD.
5. If you are using Regedt32.exe, under Data, type 0.