via email vs through email

English as a Second Language English Vocabulary, Grammar and Idioms
1

1) Send the document in an email.
2) Send the document through (an) email.
3) Send the document via (an) email.

Can someone please tell me which of the above sentences are correct? Should an be there in 2nd and 3rd sentences?

2

All should show an.

2nd sentence is not sound though.

1 and 3 are fine.

3

I would prefer:

  1. Send the document by e-mail.