We find that Purim contains many associations with “smell”. ChaZaL tell us (Megillah 7b): “A person is obligated ‘Libisumei’ on Purim until he does not ‘know’ (lo yadah) the difference between blessed is Mordichai and cursed is Haman”, in which “Libisumei” simply means “to become intoxicated”; but the word “Libisumei” is strongly connected to the word “Bisamim”, meaning “fragrances”. Thus on the level of remez, the statement can mean: “A person is obligated to be fragrant on Purim”. What is the deeper meaning behind this?

We also find that the two main characters of the Purim story, Esther & Mordichai, have names associated with smells, for Esther “is Hadassah” meaning a fragrant myrtle, and Mordichai is related to the fragrant spice used in the anointing oil (Shemos 30:23) “Mor Dror”, “pure myrrh”, which in Aramaic is: “Mor-Dachya” (Megillah 10b).

Taking a look back for a moment, we see that when Yaakov Avinu put on Eisav’s clothes in order to deceive Yitzchak and take Eisav’s blessings, first we are told that Yaakov “brought him wine and he drank” (Bereishis 27:25). Then when Yaakov drew close to be blessed by Yitzchak “he smelled the fragrance of his garments and blessed him; he said: See, the fragrance of my son is like the fragrance of a field which Hashem had blessed”.
Rashi comments: “This teaches that the fragrance of Gan Eden entered with Yaakov” -(Bereishis Rabbah 65:22). And the field that Hashem blessed is: “that He gave it a good smell, this is a field of apples (sadeh tapuchim, kabbalistically referring to Gan Eden ) - (Taanis 29b).

“Ad di’loh Yadah” (until one has no Daas): The Bnai Yissachar (mamarei Purim) teaches that out of all of man’s five senses, only one was not involved directly in the sin of eating from the original Etz HaDaas (Tree of Knowledge of Good & Evil); the sense of “Smell”.
And what kind of tree was the Etz HaDaas? According to Bereishis Rabbah (15:7) it was the Esrog Tree, which according to some is what is intended in Tanach whenever “tapuach” is mentioned and not the commonly translated “apple”. The Esrog, of the four species brought on Succos, has both Taste and Smell.

Where is Esther hinted at in the Torah? “Ve-Ani Haster Asteer Panai BaYom Hahu”, – “But I will surely have concealed My face on that day” (Deuteronomy 31:18)- (Chullin 139b). What is special about smell? With smell one can sense the presence of something which one may not be able to see, hear, taste or touch. Something that was here, or something here now. I’ve heard that studies show that memories are most strongly triggered by the sense of smell more than by any of the other senses.

The original sin caused Hashem to become greatly more concealed in the world. Man was cast out of Gan Eden, a place “Hashem blessed with a good smell”. But G-d wanted us to remember Gan Eden and make our way back, so when He sent them out “Hashem G-d made for Adam and his wife garments of skin, and He clothed them” (Bereishis 3:21). These garments where passed down from Adam to his descendents until they made their way to Yaakov (Pirkei DeR’ Eliezer 20:24) where they exhibited their smell, that reminded the blind Yitzchak of Gan Eden, and he suddenly “saw” without seeing: “See, the fragrance of my son is like the fragrance of a field which Hashem had blessed”.
What the unharmed sense of smell and the smell of Gan Eden which remained in the clothing Adam took out of Gan Eden represent is that no matter was happens, no matter how hidden Hashem becomes in the world, we can always discover Him and return to Him, sense His continual presence, even in the darkest times. Esther: “I will surely have concealed My face on that day”; Esther: “For the Conductor (G-d) on the Morning Star (ayeles hashachar)...” (Tehillim 22); The morning star, the first light of day at the end of the long night. This is Esther (Megillah 15b, Midrash Tehillim). This is the light of Mashiach (Kol HaTor 2:8). (Mashiach will judge not by sight or by hearing, but by smell (Sanhedrin 93b). Although Tehillim 22 begins with the story of G-d’s concealment it ends with our discovering Him and return to Him: “My G-d my G-d why have you forsaken me, why so far from saving me?... but ultimately “All the ends of the earth will remember and turn back to Hashem”.

Rebbi Shimon Bar Yochai taught that in the story of Purim G-d only made it appear as if He would destroy them, outwardly He hid Himself, but never intended to follow through, chas vishalom, but instead to bring about a great salvation (see Megillah 12a); “to the Jews was light!” (Esther 8:16). The light of salvation came about through Mordichai & Esther, who are both light!- Esther the Ayeles HaShachar and Mordichai ben Ya’ir, who illuminated the eyes of Yisrael (Megillah 12a). And they carried the memory and message of the fragrance of Gan Eden. (Also Esther, in Persian means Moon, which is "Yareach" in Hebrew, which contains the same letters as "Re'ach", "Smell", because through the aspect of smell one illuminates the darkness with Hashem's presence).

When we truly remember Hashem and sense His presence in all times and situations, then we undo the negative affects of the sin of the tree of knowledge of good & evil. It no longer has power over us. We recognize that good & what we might view as G-d having wronged us (“Why have you done evil (ra’ah) to this people!?” (Shemos 5:22) is a matter of perspective. There is only Hashem, and everything is ultimately for the good.

Where is Haman in the Torah? “Hamin Ha’Etz asher tzivisichah libiltee achol mimenu achalta”, “Have you eaten of the tree from which I commanded you not eat? (Bereishis 3:11) (Chullin 139b).

Putting the pieces together:

“A person is obligated to become fragrant on Purim”: To manifest their true essential nature which remains unhindered by the concealment brought about by the original sin. Instead one must remember Hashem and where he came from, and realize Hashem’s proximity to him has never really changed.

“until they no longer have Daas”: That is, they are no longer under the negative effects of the Etz HaDaas;

“which distinguishes between Blessed is Mordichai & Cursed is Haman”: and hides Hashem’s presence in the world and in our lives, making us believe that Hashem’s presence and blessing is only by the perfect and righteous, like Mordichai and that G-d is only close to those who do not sin, and that those who have eaten too often from the Etz HaDaas “which He commanded us not to eat” are cursed and dejected, “forsaken”, chas vishalom!
Leave that false reality, Sniff out the truth, “judge by smell” and you’ll see without the need to see, that there is only Hashem, and any concealment is “an outward display”.
But the inner soul knows the truth!- We smell “bisamim” during Havdalah because the soul is put at ease through smell (Berachos 44b). Through the secret of smell, that transports us back to the closeness of Hashem in Gan Eden, even now. For this we drink wine, “nichnass yayin yotzei sod”, “the wine goes in, the secret comes out”. This is why “bisumei” is both intoxication and fragrance, for one leads to the other. Drinking wine in the right amount and in the right way removes the false perception of the Etz HaDaas (which acc. to some was wine from a vine) and illuminates the truth, as R' Chayim Vital says (see Shaar Kavanos page109) that through increasing our drinking of wine on Purim, we draw forth a great light that can even illuminate the good which the forces of evil in the world have captured and distorted. Perhaps this is what is hinted at when Yitzchak was brought wine to drink and then said: “See, the fragrance of my son is like the fragrance of a field which Hashem had blessed”.

May we merit that great illumination this year, in all its manifestations.