Getting authentication error trying to send mail via smtp.office365.com

Question

We used to be able to send email via the office365 SMTP server but it quit working. It seems it stopped working about the same time we switched to usnig 2-step verification with our office365 company account, but I can't be positive on that timing,

Now we get an authentication error.

We are using a comany domain name address:

******@companydomain.com

But that is what we used previously when things worked fine.

Also used to be able to send mail using that address from a Gmail accoutn, but that also has stopped working and is also getting a authentication error.

"Server returned error: "334 VXNlcm5hbWU6 334 UGFzc3dvcmQ6 535 5.7.139 Authentication unsuccessful, user is locked by your organization's security defaults policy. Contact your administrator. [BN0PR03CA0008.namprd03.prod.outlook.com 2024-05-20T15:02:35.655Z 08DC786CB4FC7CF4] , code: 535"

Answer 1

Dear Jerry Dziuba

Have a Good day,

Thank you for posting to Microsoft Community, we are Happy to assist you.

First of all, we apologize for the trouble and inconvenience caused to your work! Based on your description I understand that you are experiencing problems with email address authentication.

To assist better you, could you please provide us with additional details?

1. May I know your affected account type or subscription (such as Microsoft365 business account, Outlook.com/Hotmail.com/live.com account or third-party account)?
2. May I know what version of Outlook do you have? What version of Outlook do I have? - Microsoft Support.

attaching relevant screenshots for your issues would be immensely helpful.

• Note: Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution.

I look forward to hearing from you!

Carmid.C-MSFT | Microsoft Community Support Specialist