SMTP virtual server reports 535+5.7.3+Authentication+unsuccessful to Office365 account RRS feed

  • Question

  • Hello - We have a SMTP virtual server on our database server that sends database notification emails - I'm unable to get emails to send successfully.  The SMTP log files shows I am getting "535+5.7.3+Authentication+unsuccessful"

    Specs are Windows Server 2012 R2, SQL Server 2017 and IIS6 plugin for SMTP Virtual Server

    • I've checked the login to office365 by going to office online, and I can login to the account.
    • Test emails sent from the database server end up in the <mailroot>\queue folder but never are deleted (sent)
    • I've tried manually adding an email test file into <mailroot>\pickup and those are immediately moved to the queue folder, where they stay
    • All of the records in the log file show the first part of the connection to Office365 but then the "535+5.7.3+Authentication+unsuccessful" result.
    • On the IIS 6 (SMTP Virtual server), I have verified the setup using this:  https://support.office.com/en-us/article/how-to-configure-iis-for-relay-with-office-365-eb57abd2-3859-4e79-b721-2ed1f0f579c9
    • I've tried changing the port from 587 to port 25 and then back again.  The same issue with the "535+5.7.3+Authentication+unsuccessful"

    Does anyone have a recommendation for what I should try next?

    Thank you,


    Tuesday, April 24, 2018 7:39 PM

All replies

  • Hi,

    Thanks for your question.

    Please try the following link to see if it helps.


    Highly appreciate your effort and time. If you have any questions and concerns, please feel free to let me know. 

    Best regards,


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    Wednesday, April 25, 2018 2:53 AM