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500 5.3.3 Unrecognized command

    Question

  • Suddenly our Exchange 2010 started posting following error. I tried to telnet to it but got this report 500 5.3.3 Unrecognized command

    It's driving me crazy, no changes has been made, also we tried to restart server still no success

    Any ideas how to solve this?

     

     

    220 mail.server.com Microsoft ESMTP MAIL Service ready at Fri, 3 Feb 2012 0

    helo mail

    250 mail.server.com Hello [10.11.10.56]

    mail from:test@test.com

    250 2.1.0 Sender OK

    rcpt to:test@domain.cm

    250 2.1.5 Recipient OK

    data

    354 Start mail input; end with <CRLF>.<CRLF>

    test

    ..250 2.6.0 <68f705c2-496d-423b-9fce-f44f50606338@server.ab.locall> [InternalId=

    14] Queued mail for delivery

     

    500 5.3.3 Unrecognized command

    .

    500 5.3.3 Unrecognized command

    .

    500 5.3.3 Unrecognized command

    .

    500 5.3.3 Unrecognized command

    .

    500 5.3.3 Unrecognized command

    .

    421 4.7.0 Too many errors on this connection, closing transmission channel

     

    Thursday, February 02, 2012 11:55 PM

Answers

  • Hi

    We configured postfix to use it only for massive mailing. Exchange is now used for company mailbox only. In some way maybe this is better to have a secondary smtp server for massive mailing, it works like a charm on CentOS, and also Exchange doesn't have so much load anymore :-)

    Thank you all for help !

    Regards,Miha

    Friday, February 10, 2012 8:36 AM

All replies

  • Any Cisco Firewall or mail guard ?

    http://support.microsoft.com/kb/320027


    Satheshwaran Manoharan | Exchange 2003/2007/2010 | Blog:http://www.careexchange.in | Please mark it as an answer if it really helps you
    Friday, February 03, 2012 12:36 AM
  • No, it's the same error when we try in LAN only PC-Exchange communication
    Friday, February 03, 2012 7:05 AM
  • Hello MihaB,

     

    If you use telnet to test from your Exchange Server, will this issue occur?

     

    How to Use Telnet to Test SMTP Communication

    http://technet.microsoft.com/en-us/library/aa995718(EXCHG.65).aspx

     

    Thanks,

     

    Evan


    Evan Liu

    TechNet Community Support

    Monday, February 06, 2012 8:43 AM
    Moderator
  • Hi

    Telnet to hub transport server works, but after mail is being queued it reports this error. I have disabled AV no Exchange, ExBPA and event logs show no errors...

     

     

    .250 2.6.0 <281fba32-33ea-402b-98a7-1a337e926f32@server.host.local> [InternalId=61] Queued mail for delivery


    500 5.3.3 Unrecognized command

    .

    500 5.3.3 Unrecognized command

    .

    500 5.3.3 Unrecognized command

    .

    500 5.3.3 Unrecognized command

    .

    500 5.3.3 Unrecognized command

    .

    421 4.7.0 Too many errors on this connection, closing transmission channel


    Monday, February 06, 2012 11:03 AM
  • On Mon, 6 Feb 2012 11:03:55 +0000, MihaB wrote:
     
    >Telnet to hub transport server works, but after mail is being queued it reports this error. I have disabled AV no Exchange, ExBPA and event logs show no errors...
    >
    >.250 2.6.0 <281fba32-33ea-402b-98a7-1a337e926f32@server.host.local> [InternalId=61] Queued mail for delivery
    >500 5.3.3 Unrecognized command
    >421 4.7.0 Too many errors on this connection, closing transmission channel
     
    Have a look at the SMTP Send protocol log. What command is it that's
    "Unrecognized" and what machine is it that's complaining about the
    command?
     
    ---
    Rich Matheisen
    MCSE+I, Exchange MVP
     

    --- Rich Matheisen MCSE+I, Exchange MVP
    Monday, February 06, 2012 10:44 PM
  • Hi

    We configured postfix to use it only for massive mailing. Exchange is now used for company mailbox only. In some way maybe this is better to have a secondary smtp server for massive mailing, it works like a charm on CentOS, and also Exchange doesn't have so much load anymore :-)

    Thank you all for help !

    Regards,Miha

    Friday, February 10, 2012 8:36 AM
  • I have seen this issue when copying and pasting several commands at once into the telnet console.  Best to type or paste individual commands to avoid such errors--which really isn't an error at all.

    Todd

    Thursday, August 15, 2013 8:04 PM