Office 365 SMTP authentication failing, even with correct account information

Anonymous
2020-02-10T16:38:43+00:00

On my Wordpress site I've run into a problem in the last day or so, where emails simply fail to send. Before today it was running flawlessly for two months. The account information/password/username etc have not changed in that two months.

I'm using a Wordpress plugin called WP Mail SMTP to facilitate the sending of all outgoing emails. The error log I'm getting from the email test on that is as follows:

Versions:

WordPress: 5.3.2

WordPress MS: No

PHP: 7.3.14-5+0~20200202.52+debian9~1.gbpa71879

WP Mail SMTP: 1.8.1

Params:

Mailer: smtp

Constants: No

ErrorInfo: SMTP Error: Could not authenticate.

Host: smtp.office365.com

Port: 587

SMTPSecure: tls

SMTPAutoTLS: bool(true)

SMTPAuth: bool(true)

Server:

OpenSSL: OpenSSL 1.1.1d 10 Sep 2019

SMTP Debug:

2020-02-10 16:36:56 Connection: opening to smtp.office365.com:587, timeout=300, options=array ()

2020-02-10 16:36:56 Connection: opened

2020-02-10 16:36:56 SERVER -> CLIENT: 220 LNXP123CA0008.outlook.office365.com Microsoft ESMTP MAIL Service ready at Mon, 10 Feb 2020 16:36:55 +0000

2020-02-10 16:36:56 CLIENT -> SERVER: EHLO www.*****.com

2020-02-10 16:36:56 SERVER -> CLIENT: 250-LNXP123CA0008.outlook.office365.com Hello [***]250-SIZE 157286400250-PIPELINING250-DSN250-ENHANCEDSTATUSCODES250-STARTTLS250-8BITMIME250-BINARYMIME250-CHUNKING250 SMTPUTF8

2020-02-10 16:36:56 CLIENT -> SERVER: STARTTLS

2020-02-10 16:36:56 SERVER -> CLIENT: 220 2.0.0 SMTP server ready

2020-02-10 16:36:56 CLIENT -> SERVER: EHLO www.zestpromotional.com

2020-02-10 16:36:56 SERVER -> CLIENT: 250-LNXP123CA0008.outlook.office365.com Hello [***]250-SIZE 157286400250-PIPELINING250-DSN250-ENHANCEDSTATUSCODES250-AUTH LOGIN XOAUTH2250-8BITMIME250-BINARYMIME250-CHUNKING250 SMTPUTF8

2020-02-10 16:36:56 CLIENT -> SERVER: AUTH LOGIN

2020-02-10 16:36:56 SERVER -> CLIENT: 334 VXNlcm5hbWU6

2020-02-10 16:36:56 CLIENT -> SERVER: c2FsZXNAemVzdHByb21vdGlvbmFsLmNvbQ==

2020-02-10 16:36:56 SERVER -> CLIENT: 334 UGFzc3dvcmQ6

2020-02-10 16:36:56 CLIENT -> SERVER: QmFkMzM4MzA=

2020-02-10 16:37:02 SERVER -> CLIENT: 535 5.7.3 Authentication unsuccessful [LNXP123CA0008.GBRP123.PROD.OUTLOOK.COM]

2020-02-10 16:37:02 SMTP ERROR: Password command failed: 535 5.7.3 Authentication unsuccessful [LNXP123CA0008.GBRP123.PROD.OUTLOOK.COM]

SMTP Error: Could not authenticate.

2020-02-10 16:37:02 CLIENT -> SERVER: QUIT

2020-02-10 16:37:02 SERVER -> CLIENT: 221 2.0.0 Service closing transmission channel

2020-02-10 16:37:02 Connection: closed

SMTP Error: Could not authenticate.

Does anyone have any ideas at all? I'm completely at a loss here.

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

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  1. Anonymous
    2021-02-24T23:58:07+00:00

    I was struggling with that too. Finally I found a solution which requires to change properties in Azure Active Directory (Properties > Manage Security Defaults). You have to turn off "Enable Security defaults" like at the linked screenshot from the documentation.

    The starting point to find that solution was **Microsoft 365 Admin Center > Settings > Org settings > Services > Modern authentication.**The link to the above mentioned documentation is provided in description of Modern authentication.

    Now I'm able to send emails by SMTP protocol with using an app password from MFA enabled account.

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  2. Anonymous
    2021-02-27T01:10:07+00:00

    Having the same problem. Has anyone found a resolution to this latest SMTP authentication problem? MS Office tells me to pay my web host to fix. Web host tells me MS 365 should fix it. Anyone from Microsoft listening?

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  3. Anonymous
    2021-02-27T10:56:11+00:00

    Have you tried the solution I've posted?

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  4. Anonymous
    2021-02-27T21:13:54+00:00

     I was struggling with that too. Finally I found a solution which requires to change properties in Azure Active Directory (Properties > Manage Security Defaults). You have to turn off "Enable Security defaults" like at the linked screenshot from the documentation.

     

    The starting point to find that solution was **Microsoft 365 Admin Center > Settings > Org settings > Services > Modern authentication.**The link to the above mentioned documentation is provided in description of Modern authentication.

     

    Now I'm able to send emails by SMTP protocol with using an app password from MFA enabled account. 

    Yes - Microsoft have made OAuth2 (the basis for Modern Authentication) a prerequisite for MFA. And it would be a bit pointless enabling MFA but leaving Basic Authentication enabled - a bit like double-locking the front door but leaving an adjacent window wide open!

    And to Mark0756's comment "MS Office tells me to pay my web host to fix", could he elaborate exactly what it says pls?

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  5. Anonymous
    2021-02-28T12:05:09+00:00

    I've been working on this the past 3 days. Recently we add multi factor security for our users and after that an inhouse application which sent emails via SMTP authentication failed to authenticate the user. I removed the MFA from the user but it didn't help. Here's how I finally solved it with the help of this thread and this one. [SOLVED] Everything using Office 365 SMTP authentication is broken, wont authenticate? - Spiceworks

    First find the reason its not authenticating. You can go into the Azure AD Admin Center-> Users->Sign Ins

    FInd the user and incident where it failed. In my case the application was "Office365 Exchange Online" The reason for failure was "

    Access has been blocked by Conditional Access policies. The access policy does not allow token issuance."

    This is a default policy that apparently is created when Modern Authentication is turned on which is a prerequisite for MFA. To get my authentication back and keep the MFA, i had to uncheck the modern authentication, create a policy for MFA sign ins.

    Uncheck modertn authentication: 365 admin center -> Settings -> org settings -> Modern authentication.

    To create conditional policies: Azure AD Admin Center->Azure AD -> Security ->Conditional Access

    • New Policy Select the users or groups , Grant -> Require MFA

    Enable policy and Save.

    This solved my specific problem.

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