Letters
Tell Mateo a little about yourself. He will write to you each week.
Letters arrive at this address. We never share or sell it.
You'll use this to sign in and read your letters.
Mateo references this in your welcome letter.
By joining, you acknowledge that Mateo Castillio is an AI persona, created and guided by the creator behind him, who directs his voice, reviews every letter, and shapes the correspondence, and that this is entertainment, not professional advice. Terms · Privacy