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

Locked Question. This question was migrated from the Microsoft Support Community. You can vote on whether it's helpful, but you can't add comments or replies or follow the question.

0 comments

48 answers

Sort by: Most helpful
Most helpful Newest Oldest
  1. Anonymous
    2021-04-02T09:48:38+00:00

    Hello @ll,

    I had the same problem with a none premium version (no access to MFA configuration).

    A very good structured answer without any needs of Powershell etc. is found here:

    https://metablogue.com/send-wordpress-emails-with-microsoft-365/

    It tells you exactly how your issue with WP Mail SMTP Plugin can be solved step by step.

    Best wishes

    inkognitus

    PS:

    When you changed your configuration, please wait about 15 - 30 minutes before you test it. Obviously it needs some time to synchronize...

    Was this answer helpful?

    2 people found this answer helpful.
    0 comments
  2. Anonymous
    2020-11-14T08:40:19+00:00

    Everything was checked but had to go open the window and then click save changes without changing anything and now SMTP works.

    Was this answer helpful?

    1 person found this answer helpful.
    0 comments
  3. Anonymous
    2020-07-25T11:05:09+00:00

    The 17th July 2020 doc Option 1 (recommended): “Authenticate your device or application directly with a Microsoft 365 or Office 365 mailbox, and send mail using SMTP AUTH client submission” confused me, and I think the confusion comes from my being unable to distinguish when the doc is referring to SMTP AUTH with Basic Authentication or SMTP AUTH with Oauth2 (or both!).

    Your comment “Regarding basic authentication … this is a protocol-based setting and it disables SMTP AUTH, regardless of whether basic auth or OAuth is being used” is a minor bombshell and confuses me further. MSFT’s original announcement was that Basic Authentication was deprecated and would be discontinued early this year, with the discontinue date then being moved to later in 2021. We were guided to replace Basic Authentication by Modern Authentication (aka Oauth2). Your comment above implies that EITHER form of authentication* is deprecated – that SMTP itself will be blocked! If so, what is the recommended replacement?

    * to be pedantic: for ‘Oauth2’ read openid authentication with Oauth2 authorisation

    Was this answer helpful?

    1 person found this answer helpful.
    0 comments
  4. Anonymous
    2020-05-30T19:02:58+00:00

    I have the same problem.

    I have two org, one that works and one that doesn't.

    Both are using MFA.

    The one that doesn't work was created recently (April 2020). Tried App passwords, disabling MFA, resetting passwords, creating new users. Nothing works.

    Was this answer helpful?

    1 person found this answer helpful.
    0 comments
  5. Anonymous
    2020-05-28T18:01:45+00:00

    I am experiencing exactly the same trouble. Please let me know if anyone finds a solution to this.

    Was this answer helpful?

    1 person found this answer helpful.
    0 comments