rfc2193.txt

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   determining which server the mailbox should be created on.

   Example:

      C: A001 CREATE "SHARED/FOO"
      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/FOO]
         Mailbox should be created on remote server

   Alternatively, because a home server is required to maintain a
   listing of referred remote mailboxes, a server MAY allow the creation
   of a mailbox that will ultimately reside on a remote server against
   the home server, and provide referrals on subsequent commands that
   manipulate the mailbox.

   Example:

      C: A001 CREATE "SHARED/FOO"
      S: A001 OK CREATE succeeded

      C: A002 SELECT "SHARED/FOO"
      S: A002 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/FOO]
         Remote mailbox.  Try SERVER2





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4.3. RENAME Referrals

   An IMAP4 server MAY respond to the RENAME command with one or more
   pairs of IMAP mailbox referrals.  In each pair of IMAP mailbox
   referrals, the first one is an URL to the existing mailbox name and
   the second is an URL to the requested new mailbox name.

   If within an IMAP mailbox referral pair, the existing and new mailbox
   URLs are on different servers, the remote servers are unable to
   perform the RENAME operation.   To achieve the same behavior of
   server RENAME, the client MAY issue the constituent CREATE, FETCH,
   APPEND, and DELETE commands against both servers.

   If within an IMAP mailbox referral pair, the existing and new mailbox
   URLs are on the same server it is an indication that the currently
   connected server is unable to perform the operation.  The client can
   simply re-issue the RENAME command on the remote server.

   Example:

      C: A001 RENAME FOO BAR
      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER1/FOO
              IMAP://user;AUTH=*@SERVER2/BAR] Unable to rename mailbox
              across servers

   Since the existing and new mailbox names are on different servers,
   the client would be required to make a connection to both servers and
   issue the constituent commands require to achieve the RENAME.

   Example:

      C: A001 RENAME FOO BAR
      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/FOO
              IMAP://user;AUTH=*@SERVER2/BAR] Unable to rename mailbox
              located on SERVER2

   Since both the existing and new mailbox are on the same remote
   server, the client can simply make a connection to the remote server
   and re-issue the RENAME command.

4.4. COPY Referrals

   An IMAP4 server MAY respond to the COPY command with one or more IMAP
   mailbox referrals.  This indicates that the destination mailbox is on
   a remote server.  To achieve the same behavior of a server COPY, the
   client MAY issue the constituent FETCH and APPEND commands against
   both servers.




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   Example:

      C: A001 COPY 1 "SHARED/STUFF"
      S: A001 NO [REFERRAL IMAP://user;AUTH=*@SERVER2/SHARED/STUFF]
              Unable to copy message(s) to SERVER2.

5.1 RLIST command

   Arguments:  reference name
               mailbox name with possible wildcards

   Responses:  untagged responses: LIST

   Result:     OK - RLIST Completed
               NO - RLIST Failure
               BAD - command unknown or arguments invalid

   The RLIST command behaves identically to its LIST counterpart, except
   remote mailboxes are returned in addition to local mailboxes in the
   LIST responses.

5.2 RLSUB Command

   Arguments:  reference name
               mailbox name with possible wildcards

   Responses:  untagged responses: LSUB

   Result:     OK - RLSUB Completed
               NO - RLSUB Failure
               BAD - command unknown or arguments invalid

   The RLSUB command behaves identically to its LSUB counterpart, except
   remote mailboxes are returned in addition to local mailboxes in the
   LSUB responses.

6. Formal Syntax

   The following syntax specification uses the augmented Backus-Naur
   Form (BNF) as described in [ABNF].

   list_mailbox = <list_mailbox> as defined in [RFC-2060]

   mailbox = <mailbox> as defined in [RFC-2060]

   mailbox_referral = <tag> SPACE "NO" SPACE
      <referral_response_code> (text / text_mime2)
      ; See [RFC-2060] for <tag>, text and text_mime2 definition



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   referral_response_code = "[" "REFERRAL" 1*(SPACE <url>) "]"
      ; See [RFC-1738] for <url> definition

   rlist = "RLIST" SPACE mailbox SPACE list_mailbox

   rlsub = "RLSUB" SPACE mailbox SPACE list_mailbox

6. Security Considerations

   The IMAP4 referral mechanism makes use of IMAP URLs, and as such,
   have the same security considerations as general internet URLs [RFC-
   1738], and in particular IMAP URLs [RFC-2192].

   With the MAILBOX-REFERRALS capability, it is potentially easier to
   write a rogue server that injects a bogus referral response that
   directs a user to an incorrect mailbox.  Although referrals reduce
   the effort to write such a server, the referral response makes
   detection of the intrusion easier.

7. References

   [RFC-2060], Crispin, M., "Internet Message Access Protocol - Version
   4rev1", RFC 2060, University of Washington, December 1996.

   [RFC-2192], Newman, C., "IMAP URL Scheme", RFC 2192, Innosoft,
   September 1997.

   [RFC-1738], Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
   Resource Locators (URL)", RFC 1738, CERN, Xerox Corporation,
   University of Minnesota, December 1994.

   [RFC-2119], Bradner, S., "Key words for use in RFCs to Indicate
   Requirement Levels", RFC 2119, Harvard University, March 1997.

   [ABNF], DRUMS working group, Dave Crocker Editor, "Augmented BNF for
   Syntax Specifications: ABNF", Work in Progress, Internet Mail
   Consortium, April 1997.

8.  Acknowledgments

   Many valuable suggestions were received from private discussions and
   the IMAP4 mailing list.  In particular, Raymond Cheng, Mark Crispin,
   Mark Keasling, Chris Newman and Larry Osterman made significant
   contributions to this document.







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9. Author's Address

   Mike Gahrns
   Microsoft
   One Microsoft Way
   Redmond, WA, 98072

   Phone: [phone]
   EMail: [e-mail]










































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