...What race was he? An elf? As a human Sauron would've had to change his Mouth every 60 years or so, since even the Valar cant tke away the Gift of Eru, that is mortality for men...
"The Lieutenant of the Tower of Barad-dûr he was, and his name is remembered in no tale; for he himself had forgotten it, and he said: ‘I am the Mouth of Sauron.’ But it is told that he was a renegade, who came of the race of those that are named the Black Númenóreans; for they established their dwellings in Middle-earth during the years of Sauron’s domination, and they worshipped him, being enamoured of evil knowledge. And he entered the service of the Dark Tower when it first rose again, and because of his cunning he grew ever higher in the Lord’s favour; and he learned great sorcery, and knew much of the mind of Sauron; and he was more cruel than any orc." FOTR, LOTR
So you see the Mouth of Sauron was said to have been one of the Black Numenoreans, and his true name is known to no-one save probably only Sauron.
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Utúlie'n aurë! Aiya Eldalië ar Atanatári, utúlie'n aurë! Auta i lómë! Aurë entuluva!
indeed Sauron had to change the lieutenant of Barad-dur...I wonder if he made an audition for it... I can imagine Sauron...Thanks, we'll call you back... But indeed, since Sauron's return to Mordor he was the only one to have this position as shown in the quote however you make one mistake, the mouth of sauron wa not a normal man, such as for example the Rohirrim he was a Numenorean, and so, even though serving an evil power he still had a longer life then most men and as proof: the words "when it first rose again" reffer to the year 2951, as that is when Barad-dur was rebuilt so in the year 3019, mos was at least 68 years old, but as he didn't enter the service of Sauron at birth he was probably older then 90