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.
SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

Hello Adam,

Given this situation, I consider you may login Outlook Web App with impacted account to see if emails can be sent.

If Outlook Web App works well, then check firewall settings, anti-virus or related apps on your server and network, make sure all Office 365 related traffics are allowed: Office 365 URLs and IP address ranges, for some SMTP relay issues are caused by network settings.

You may also refer to this article for troubleshooting: Fix issues with SMTP client submission.

Besides, is there any organization-wide changes made recently? If convenient, use a different Office 365 account to see how it goes.

Best Regards,

--------* Beware of Scammers posting fake Support Numbers here. SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation. SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

Hello Adam,

Given this situation, I consider you may login Outlook Web App with impacted account to see if emails can be sent.

If Outlook Web App works well, then check firewall settings, anti-virus or related apps on your server and network, make sure all Office 365 related traffics are allowed: Office 365 URLs and IP address ranges, for some SMTP relay issues are caused by network settings.

You may also refer to this article for troubleshooting: Fix issues with SMTP client submission .

Besides, is there any organization-wide changes made recently? If convenient, use a different Office 365 account to see how it goes.

Best Regards,

Hello Anna,

I'm having the exact same issue currently.

I have an older account (from January 2020, which is working perfect).
I just got a new account & domain today, and for that one I get exactly the same error as Adam. I checked with the hosting provider, and no blocks at their end - so this is very strange. How should I go about it?

SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

I bought an email with Godaddy last night, using Office 365, so that I could use it for SMTP on my Wordpress site.  Same problem as these others -- the SMTP will not authenticate:

SMTP ERROR: Password command failed: 535 5.7.3 Authentication unsuccessful [MN2PR04CA0007.namprd04.prod.outlook.com]

I even changed passwords, to no avail.  Nothings works.  I think I need a refund.

SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation. SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

I'm having the same problem, I've got a ticket open with Microsoft support but so far nothing. IMAP works fine, just SMTP that doesn't accept the password. I've tried 5 different accounts, we are using a mix of E1 licenses and I'm wondering if there is any new security applied by Microsoft that we are not aware and is blocking access. I'm not using MFA on the account, so I cannot create an app password for that purpose.

Someone help us please!

SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation. SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation. SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation. SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.

I am also getting authentication issues. I am able to log onto the web app with the same credentials.

I tried using OSX email app, Spark, and it will not work.  I am trying to also send email via PHP using 'PHPMailer' as well as "Pear Mail'.

nothing seems to work. Is there something that needs to be enabled on outlook.live.com???

SPAM/Advertising Virus/Spyware/Malware danger Other Term of Use or Code of Conduct violation Child exploitation or abuse Harassment is any behavior intended to disturb or upset a person or group of people. Threats include any threat of suicide, violence, or harm to another. Any content of an adult theme or inappropriate to a community web site. Any image, link, or discussion of nudity. Any behavior that is insulting, rude, vulgar, desecrating, or showing disrespect. Any behavior that appears to violate End user license agreements, including providing product keys or links to pirated software. Unsolicited bulk mail or bulk advertising. Any link to or advocacy of virus, spyware, malware, or phishing sites. Any other inappropriate content or behavior as defined by the Terms of Use or Code of Conduct. Any image, link, or discussion related to child pornography, child nudity, or other child abuse or exploitation.