This is easier to figure out than you think. If someone has your phone or Mac, then they have your text messages and email. If not, it’s a different story. Jefferson Graham:
Encryption, says Apple on its website, is used to protect trillions of online transactions every day, for shopping, paying bills and communicating with programs like its own iMessage or FaceTime, or Facebook’s Whatsapp. Encryption, says Apple, “turns your data into indecipherable text.”
Messages are encrypted. Email is not (usually).