These are the possible phrasings I would use: "I've sent you an email, at [email protected]" "I've sent an email to you, at "[email protected]" "I've sent an email to [email protected]" "I've sent you an email." "I've sent an email to you." I don't think "I've sent you an email TO [email protected]" is very wrong, but it is not commonly used. It is more common to use "AT" in that sentence." My guess is because when we say "I've sent you an email", it is a shortened but accepted form of "I've sent TO you an email". Hence, put together, it would become "I've sent TO you an email TO [email protected]" and the use of 2 "TO"s so close together sounds a little strange even if the first "to" was sort of omitted. Of course there is an exception when the second "to" is a part of an infinitive verb (i.e. TO run, TO eat, TO sleep) (e.g. "I've sent (to) you an email TO TELL you the details of the party.") in this case, it sounds natural because it is not a preposition in this case. It is an infinitive verb. Hope this helps! :)

I hear both and feel like they are equally correct.

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