Rashi: It is Koresh Melech Paras ¹ . The Gematriya of Koresh (520) is the same as that of Daryavesh. We say (Rosh Hashanah 3b) that Koresh, Daryavesh and Artachshasta are all one. He is called Koresh for he was a Kosher king, He is called Artachshasta due to the kingship. Seder Olam says that Daryavesh is Artachshasta. The entire kingship is called Artachshasta.

Malbim #2: The one who says that Artachshasta was a different name, we must say that the building did not cease until after Koresh died, and Artachshasta became king. The building ceased [at least] 14 years - these are the Shavu'im mentioned in Daniel (9:25), according to my Perush.

Rashi: He wrote matters of Shalom in his letter.

Malbim: Bi'Shlam is a name of one of the Tzarei Yehudah and Binyamin. He wrote...

Rashi: It is the name of a man among Tzarei Yehudah and Binyamin.

Rashi: His friends and entourage.

Rashi: He wrote El (to) Artachshasta.

Rashi: The writing of the letter.

Ibn Ezra #1: The forms of the letters are read in our language - "El ha'Yehudim ki'Chsavam."

Ibn Ezra #2: This Sefer is equal in its Kesav (character set) and language - both are Arame'ic ¹ .

Ibn Ezra #3: It is a stamped (with a signet). This is the correct Perush.

Malbim: The writing had to be translated and equated to the initial letter in Arame'ic (refer to 4:8:2:2).

Rashi: The letters were in Arame'ic, and the writing was in Arame'ic language.

Malbim: The letter was in Arame'ic, and had to be translated from Arame'ic to Persian (refer to 4: 8:2:2).