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RFC 1957

                 Some Observations on Implementations
                   of the Post Office Protocol (POP3)


   Sometimes an implementation is mistaken for a standard.  POP3 servers
   and clients are no exception.  The widely-used UCB POP3 server,
   popper, which has been further developed by Qualcomm, always has
   additional information following the status indicator.  So, the
   status indicator always has a space following it.  Two POP3 clients
   have been observed to expect that space, and fail when it has not
   been found.  The RFC does not require the space, hence this memo.
   These clients are the freely copyable Unix "popclient" and the
   proprietary "netApp Systems Internet Series".  The authors of both of
   these have been contacted, and new releases will not expect the
   space, but old versions should be supported.

   In addition, two popular clients require optional parts of the RFC.
   Netscape requires UIDL, and Eudora requires TOP.

   The optional APOP authentication command has not achieved wide
   penetration yet.  Newer versions of the Qualcomm POP server implement
   it.  Known client implementations of APOP include GNU Emacs VM client
   and Eudora Lite and Eudora Pro.

Security Considerations

   Security issues are not discussed in this memo.


   [1]  Myers, J., and M. Rose, "Post Office Protocol - Version 3",
        STD 53, RFC 1939, May 1996.

Nelson                       Informational                      [Page 1]

RFC 1957 Notes on POP3 Implementations June 1996 Author's Address Russell Nelson Crynwr Software 521 Pleasant Valley Rd. Potsdam, NY 13676 Phone: +1.315.268.1925 FAX: +1.315.268.9201 EMail: nelson@crynwr.com

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