535: 5.7.3 Authentication unsuccessful

Anonymous
2020-04-16T10:47:36+00:00

Hello,

I have an issue when using an O365 account and sending emails from an application.

The application has been suitable to use tls/starttls, port 587, ect.

When entering an email account and password, the following message occurs:

"535: 5.7.3 Authentication unsuccessful"

I would like to understand, what are the mininal features of an O365 account so that it can be used from another application.

I have performed different tests, which allow me to indicate that the account is Ok.

Thank you.

Microsoft 365 and Office | Subscription, account, billing | For home | Windows

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  1. Anonymous
    2020-05-25T14:02:03+00:00

    the same problem here. hope there will be a fix!

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  2. Anonymous
    2020-05-29T15:10:48+00:00

    Hi All,

    please check your MX entry.  It should be like domainname**.mail.protection.outlook.com**

    This means as SMTP server use domainname**.mail.protection.outlook.com**with port 25.

    I hope this helps.

    Best regards

    Chris

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  3. Anonymous
    2020-06-01T09:43:25+00:00

    HI Chris,

    We have this MX entry for our domain apicalsolutions.com

    apicalsolutions.com. MX (10) apicalsolutions-com.mail.protection.outlook.com.

    Is this correct? If yes then it is still not working. 

    Best Regards

    Vishwas

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  4. Anonymous
    2020-06-01T12:04:06+00:00

    HI Chris,

    We have this MX entry for our domain apicalsolutions.com

    apicalsolutions.com. MX (10) apicalsolutions-com.mail.protection.outlook.com.

    Is this correct? If yes then it is still not working. 

    Best Regards

    Vishwas

    Hi Vishwas,

    so you should use as SMTP server: apicalsolutions-com.mail.protection.outlook.com with port 25.

    As user use any user of your domain. Even if it has no linked mailbx you can use it for login.

    Usually it should work.

    https://docs.microsoft.com/de-de/exchange/mail-flow-best-practices/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-office-3#settings-for-direct-send

    Do you get any error message?

    Best regards

    Chris

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  5. Anonymous
    2020-06-01T12:34:49+00:00

    Hi Chris,

    We are getting following error

    AuthenticationInvalidCredentials: 5.7.3 Authentication unsuccessful [DB6PR07CA0108.eurprd07.prod.outlook.com]

    But the credentials are all correct. We tried with several accounts. 

    Best Regards,

    Vishwas

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