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Undelivered Mail: 501 Syntax error in parameters or arguments

Hello everybody,

we send and receive mail via sophos central
We have been receiving the following message more and more frequently for about 1 week:

"host ***** refused to talk to me: 501 Syntax error in parameters or arguments"

The message does not only come from a recipient/host. Other senders can then successfully deliver to this recipient/host.

In the last report, we have now found out that it was sent by a sophos node that is on a blacklist. but then should the error message look different?

 

best regards

Tolik



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  • Hi  

    Are you able to send Emails to other servers without any issues? The error 501 mostly occurs due to an invalid email address, but it can also be associated with connection problems sometimes.

    Regards

    Jaydeep

  • Hi there,
    
    Yes, I can send to others.
    
    It is strange that one colleague can send to this address and the other receives 501 errors. 

    And at some point the colleague can also send the error 501 to the recipient. The error has been around for about 1 week. Before this did not come ...
  • Hi  

    That does not seem to be an issue from Central to be honest. Are you still seeing the NDR emails?

    Regards

    Jaydeep

  • Hi all,

    We do face the same issue of 501 error.

    At least once a day ( 3000+ Mails/day out are fine) we receive an error like:  host mail.xxx.yyy [134.93.xxx.yyy] refused to talk to me: 501 Syntax error in parameters or arguments

     

    I was wondering about the subject :  date:subject:to:from;

    within the error report message.

     

    I did check reputation of domain/IP, BL, MX etc. but no issues found.

     

    Any help or info more then appreciated

     

  • FormerMember
    0 FormerMember in reply to BH_EDV1

    Hi  

    Did you see this email in central email gateway mail logs? If yes, please provide the message-id. Could you please share the sample email via PM? 

    Thanks,

  • I have the same issue and believe that through transport some mail header fields are being shiftet. I had a support case open but that did not lead to any solution as they just blamed the recipient server to cut the connection.

    Also the subject line "date:subject:to:from;" shows that there is something messed up with the header fields.

    Did anyone find a solution to this?