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Network Working Group                                          R. Nelson
Request for Comments: 1957                               Crynwr Software
Updates: 1939                                                  June 1996
Category: Informational

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

Status of this Memo

   This memo provides information for the Internet community. This memo
   does not specify an Internet standard of any kind. Distribution of
   this memo is unlimited.


   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

Nelson                       Informational                      [Page 2]