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M19B66's avatar
M19B66
Brass Contributor
Feb 09, 2023

SMTP XOAUTH suddenly failing for Outlook personal with '535 5.7.3 Authentication unsuccessful'

Please see here for the details:

 

https://techcommunity.microsoft.com/t5/outlook/smtp-xoauth-suddenly-failing-for-outlook-personal-with-535-5-7-3/m-p/3734392

 

Note that this is about personal accounts for which SMTP AUTH cannot be disabled, and that this worked fine for existing setups/configuration until the end of January.

 

In other words, this is not something which can be resolved by changing configurations or software, and therefore is rather likely a problem with the Outlook SMTP server.

 

 

identity and access management

6 Replies

    • TowHitch's avatar
      TowHitch
      Copper Contributor
      May 15, 2023
      It seems like Microsoft have quietly resolved this issue, it has suddenly started working for us. https://learn.microsoft.com/en-us/answers/questions/1168242/smtp-send-oauth-permission-not-working-for-consume
      • Enzo_Tech's avatar
        Enzo_Tech
        Copper Contributor
        May 16, 2023
        Yes, it seems there was a mystery fix happened on MS side. 🙂
        Anyway, due to this issue I was able to produce a Test Tool written in Rust Programming Language just to test this workflow. https://github.com/LorenzoLeonardo/microsoft-smtp-xoauth2-test-tool
  • Enzo_Tech's avatar
    Enzo_Tech
    Copper Contributor
    Apr 14, 2023

    I also confirmed that until now it is not working.

    535 5.7.3 Authentication unsuccessful [SJ0PR13CA0189.namprd13.prod.outlook.com 2023-04-14T01:41:59.958Z 08DB3BD5C46109BA]

    I am using offline_access and SMTP.Send as scope via Device Code Flow
    These are the endpoints that I used to get exchange device code for an access token to be able to send email using consumer accounts using oauth2

    device_endpoint = "https://login.microsoftonline.com/common/oauth2/v2.0/devicecode",
    token_endpoint = "https://login.microsoftonline.com/common/oauth2/v2.0/token"

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