When one sends Mishloach Manot, must he send each food item in a separate package?
The Ben Ish Chai (Rabbi Yosef Chayim of Baghdad, 1833-1909), in his work "Torah Li'Shma," writes that one must, indeed, package the foods sent for Mishloach Manot separately. He explains that the obligation of Mishloach Manot requires sending two items to one's fellow, and two foods in a single basket are considered a single gift, rather than two distinct gifts. In the context of Shabbat, for example, one who carries a basket containing numerous objects is considered to have transgressed Shabbat only once, since all the items are deemed a single entity. Similarly, two items in a Mishloach Manot basket are seen as just one item, and thus the obligation of Mishloach Manot requires sending the two foods in separate packages.
Chacham Ovadya Yosef, however, disagrees with the Ben Ish Chai's position, and rules that one can fulfill the obligation by sending a single basket containing different food items. He argues that the laws of Shabbat have no bearing on the obligation of Mishloach Manot, which requires simply that one's fellow receives from him two food items. Regardless of whether the foods are packaged together or separately, one fulfills the obligation if his fellow receives from him two items.
Therefore, although those who wish to be stringent in this regard should be commended, one who wishes to send a single package containing multiple foods may do so without concern.
The Ben Ish Chai also mentions (listen to audio for precise citation) that one should wear Shabbat clothing or other formal attire on Purim, rather than wearing weekday attire, given that Purim marks a very momentous occasion for the Jewish people.