In your title, you used the verb “is”, but in your question, you used the verbs “give” and “send”. This changes everything. We say “to” if the gift is actually moving, so when you give or send the gift to me, we say “to”. However, if the gift just “is”, without moving, then we use “for” — “This is a gift for you. I’ll send it to you by mail. By the way, this is the same in Spanish. (I actually imagined you were a Brazilian-Portuguese speaker when I saw your question.) Es un regalo para ti. Te lo envío (a ti) por correo. Let me know if my answer helped you.

To or for will be triggered by the verb and also the context so it's difficult to answer without an exact sentence.