[Samba] user access with email format

[Jose Antonio Valero]

Hello, I have set up a Samba AD domain in version 4.21, that domain has
created a trust relationship with a Windows Server 2016 AD. If I access a
computer from the Samba domain with a user from the Windows domain with
domain\user format, I access without problems, however, if I access
user at domain.com it never lets me access.  What am I doing wrong?
Thank you very much and greetings
-- 
José Antonio Valero
javalero at gmail.com