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to have someone send (a message, parcel, etc.); to send (via someone else); to leave (a message) with someone
「託ける」 has another reading with different meanings.
友人に手紙を託けて届けてもらった。
I had a friend deliver the letter for me.
出張の同僚にお土産を託けた。
I asked a colleague on a business trip to bring a gift.
友人に手紙を託けるよう頼んだ。
I asked a friend to deliver a letter.