E-Mail tool cannot sign onto M365 over SMTP

Bühler Gabriel 76 Reputation points

Hello Everyone

We are currently having an issue when one of our partners is trying to Send E-Mail over SMTP. He receives the following error:

User's image

He is able to connect to M365 over Telnet TCP 587 on the Server he is trying to sign into M365 with the tool they are using. Do you may know what the issue could be?

Thank you for your help.

Kind regards,


Microsoft 365
Microsoft 365
Formerly Office 365, is a line of subscription services offered by Microsoft which adds to and includes the Microsoft Office product line.
4,275 questions
Microsoft Exchange Online
{count} votes