via email vs through email

[Daemon99]

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?
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Non-native speaker of English
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I intend to live forever - so far, so good.

[Kitosdad]

All should show an.

2nd sentence is not sound though.

1 and 3 are fine.
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If you need me, I'm here.

[Jamie (K)]

I would prefer:

4) Send the document by e-mail.