DOCUMENT:Q194742 13-MAY-2000 [exchange] TITLE :XFOR: Internet Mail Service Support for user@[IP Address] Format PRODUCT :Microsoft Exchange PROD/VER:winnt:5.5 OPER/SYS: KEYWORDS:exc55 ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Exchange Server, version 5.5 ------------------------------------------------------------------------------- SUMMARY ======= In Exchange Server versions 4.0 and 5.0, it is not possible to send messages to a user by using the following format: user@[IP Address] However, in accordance with for Request for Comments (RFC) 821 and 821bis, this is a valid addressing format. Microsoft recognizes the need for compliance to this RFC specification. Microsoft Exchange Server version 5.5 allows for this addressing method and therefore allows messages to be sent by using this format. The feature involves a modification to the Exchange Server Internet Mail Service to understand IPv4 literals. The Internet Mail Service is now capable of accepting mail inbound, delivering outbound, and rerouting mail addressed in the format "user@[IP Address]," also known as IPv4 literal. NOTE: The admin does not allow you to create a proxy of the form 'user@[IP Address]' (it strips the brackets). For additional information, click the article number below to view the article in the Microsoft Knowledge Base: Q193316 XFOR: How to create addresses of form 'user@[IP Address] MORE INFORMATION ================ Per RFC 821 page 31: Hosts are generally known by names, which are translated to addresses in each host. Note that the name elements of domains are the official names -- no use of nicknames or aliases is allowed. Sometimes, a host is not known to the translation function and communication is blocked. To bypass this barrier, two numeric forms are also allowed for host "names". One form is a decimal integer prefixed by a pound sign, "#", which indicates the number is the address of the host. Another form is four small decimal integers separated by dots and enclosed by brackets, for example, "[123.255.37.2]", which indicates a 32-bit ARPA Internet Address in four 8-bit fields. NOTE: The other message format that is noted in this section of RFC 821 is the following user@#xxxxxxxxx where xxxxxxxx is a decimal number that corresponds to the host address of the computer. The Internet Mail Service on all versions of Exchange Server including Exchange 2000 Server does not support this type of addressing. Additional query words: IPv4-literal, RFC821, 821bis ====================================================================== Keywords : exc55 Technology : kbExchangeSearch kbExchange550 kbZNotKeyword2 Version : winnt:5.5 Issue type : kbinfo ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2000.