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Apr 03 2024, 07:00 AM - 11:00 AM (PDT)
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SMTP XOAUTH suddenly failing for Outlook personal with '535 5.7.3 Authentication unsuccessful'

Copper Contributor

Please see here for the details:


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.



6 Replies

I also confirmed that until now it is not working.

535 5.7.3 Authentication unsuccessful [ 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 = "",
token_endpoint = ""

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.

@Enzo_Tech Is this issue fixed now i tried testing SMTP Xoauth with my outlook personal account. Iam getting the same error. If it is fixed can you help me the solution?



Hello yes it is now working please check the scope used under providers in my sample test tool written in Rust Programming language