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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.

Observations

 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.

References

 [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]