What is the difference between logging in when connecting via RDP domain.ad\user and [email protected]?

Question

Active Directory

So, people connect via rdp to work from home. In most cases, they connect according to the scheme: domain.ad\user, but this does not work for everyone. Shows invalid username/password.
In the minority, they connect with the line in the user: [email protected] Tell me
why this is happening, how do these options differ?

Answer 1

and they are connected by different clients? or everyone sits on Windows and connects with one mstsc client

Answer 2

domain.ad\user - UPN name
[email protected] - UPN name
use Down-Level Logon Name (NetBIOS):
domain\user The
difference is which service is responsible for primary authorization.