POP3, first response is always "-ERR Protocol error. 17"


  • I have quite a strange issue on an Exchange 2010 server trying to enable and use POP3 access to any mailbox. When I telnet on port 110 to the server the first response to any command is always "-ERR Protocol error. 17" after that the commands are processed correctly:

    +OK The Microsoft Exchange POP3 service is ready.
    -ERR Protocol error. 17

    +OK The Microsoft Exchange POP3 service is ready.
    user someuser
    -ERR Protocol error. 17
    user someuser

    How can I disable this "feature?" No email client I have tested appears compatible with this arrangement.

    Thursday, March 22, 2012 4:49 AM

All replies

  • Hi Andreas,

    Suggest you install the latest service pack and rollup for Exchange 2010 (Exchange 2010 SP2 ru1) in order to avoid some known issues first.

    What's the error message when users open Outlook via POP3?

    Please check whether there is any relevant event logs in the Event Viewer.

    Frank Wang

    TechNet Community Support

    Friday, March 23, 2012 8:09 AM
  • Any follow-up to this issue?  I am seeing the EXACT same thing, where the first command gets rejected with Protocol error -17, then works fine after that.  Could this be a bug in 2010 SP2 RU1?


    UPDATE : Just installed RU2 and that does not solve this issue.
    • Edited by cliess Wednesday, April 18, 2012 3:33 PM
    Wednesday, April 18, 2012 12:36 PM
  • Hi there Craig,

    Its 2014 already for me. Did you ever find a solution for your problem?

    I am looking at the same thing.



    Monday, March 31, 2014 10:08 AM
  • I saw that when you use the tool PUTTY in raw mode, then it does not show this error.
    • Proposed as answer by Alex777_01 Monday, March 31, 2014 10:29 AM
    Monday, March 31, 2014 10:28 AM