Something like testuser@test.local should be a match. The regex I use is:
\w[\w\.\- ]*$/@/^[a-zA-Z][a-zA-Z0-9\-\.]{0,61}[a-zA-Z]
What did I miss?
It's not like an E-Mail because it can be many sublevels in the domain e.g. test.local.country.city.street