Office 365 does not send mails

Please check that SMTP sending via the specified account is permitted (this is not standard for Office 365 and must be activated: In the Microsoft 365 Admincenter, go to Active users and select the relevant user. In the Email tab, go to Manage email apps. There you activate the option Authenticated SMTP) In addition, you can check the server logs to see which error message is generated for this - in many cases the solution is already visible there - possible problems from support cases were: missing activations by firewalls, missing libraries, missing authorizations, e-mail dispatch deactivated on the server.