The letter from Tofugu was just delivered.
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means deliver so the verb vocab version here is to be delivered or to arrive. You know this one is "to be delivered" (aka it's just getting delivered, you aren't doing the delivery) because when this item arrives at your house you say "coo'" (く), it arrived.
The reading is the one you learned with the kanji: とど!