' via email' is used by native speakers: Example: You can contact me via email.

I have never seen per email and consequently I would never use that expression. Via email is OK. What about 'by email'?

Adrienne, One of the definitions of "per" is "by or through the means of". Expressions such as "per post", "per rail", "per express" and the like are grammatically correct, although you don't come across them very often because they are older expressions. By extension "per email" is proper usage. "Via" meaning "through the medium of" is also correct in "via email", as is "by email". In medicine the use of "per" meaning "by or through the means of" is common, for instance, "per the bloodstream". I suggest a comprehensive international dictionary such as The Merriam Webster Unabridged, or The Oxford English Dictionary, where you are more likely to find less common and older definitions of many words.

I know that via Email is correct. "Per" is often used with "day" for example per day, per year.

'per email' is correct but uncommon - in this usage it certainly means 'by means of'. 'as per' is a common phrase meaning 'in accordance with' and you could say 'as per your email' referring to the contents/meaning of the email