PPP domain authentication issue

Hello all.
we use mikrotik as vpn server with AD authentication on Windows server.
We have separate donains in our forest, so we faced the issue:
When user types his login user@example.com it goes through good.
But when used “Automatically use my Windows logon name” in VPN client settings or user use EXAMPLE\user format (which is same)
Mikrotik sends to Radius and shows in log only user without domain.
Which does not happen with windows VPN server.
Looks like it just ignore everything before backslash ""
Has anyone same issue and solved it?