Answer 1

I guess this is not what you are looking for.
These e.g. would match:
[e-mail]
[e-mail]

You get one word-character, then a digit in front of the @ and one word-character behind.

There are slight different patterns. Here one from MSDN:
^(?(")(".+?(?<!\\)"@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-0-9a-z]*[0-9a-z]*\.)+[a-z0-9][\-a-z0-9]{0,22}[a-z0-9]))$

You see, they are pretty complicated. But you find a good step-by-step explanation to it on MSDN, too:
https://docs.microsoft.com/en-us/dotnet/standard/base-types/how-to-verify-that-strings-are-in-valid-email-format