certified letter(If a letter is sent by certified mail, the person who receives it must sign their name to show that it has been received. cambridge dictionary amatsyuk)
with acknowledgment due(Только для направления АНГЛ ⇒ РУС, потому что не ручаюсь за "английскость" источника: взято из договора Европейской Комиссии, а гуглится вообще только по индийским сайтам). Но вариант втретился: All notice or other communication given pursuant to this Agreement must be ... sent by registered mail with acknowledgment due 4uzhoj)
advice of delivery(GB: ...letter advice of delivery or equivalent, stating the nature, probable duration and ; foreseeable effects. Notice is given by registered letter with advice of delivery or equivalent procedure. Alexander Demidov)
