פירוש על אסתר 9:19

Unwalled. Who do not reside in walled cities, [celebrate] on the fourteenth, and those who reside in walled cities [celebrate] on the fifteenth, like Shushan; and [these cities] must have been surrounded [by walls] since the days Yehoshua Bin Nun. So did our Rabbis expound and learn.⁴Maseches Megillah 2b. Shushan which was without a wall in the time of Yehoshua was accorded special status “because the miracle was performed there.”

Sending. This מִשְׁלֹחַ is a noun like מִשְׁמָר [guarding]⁵Nechemyah 12:24. and מִשְׁמָע [hearing],⁶Yeshayah 11:3. therefore the shin is vowelized softly [without a dagesh].