RAMBAM, who is considered a sage of Israel and who's codification of Jewish law is universally recognized by all modern strains of Orthodox Judaism (including Chassidic and Mitnagdim, Yeshivish and Litvish), clearly states that one who denies the coming of Moshiach is an apostate, a heretic, and outside of Jewish faith... From his masterpiece work, Mishneh Torah, here are some of the laws concerning Moshiach.
http://www.chabad.org/library/moshiach/article_cdo/aid/101744/jewish/Laws-Concerning-Kings-and-the-Messiah.htmMISHNEH TORAH: Hilchot Melachim Laws Concerning Kings
Chapter XI1. The Messianic King will arise in the future and restore the Davidic Kingdom to its former state and original sovereignty. He will build the Sanctuary1 and gather the dispersed of Israel.2 All the laws will be re-instituted in his days as they had been aforetimes;3 sacrifices will be offered, and the Sabbatical years and Jubilee years will be observed4 fully as ordained by the Torah.5
Anyone who does not believe in [Mashiach], or whoever does not look forward to his coming,6 denies not only [the teachings of] the other prophets but [also those] of the Torah and of Moses our Teacher. For the Torah attested to him, as it is said:
“G-d, your G-d, will return your captivity and have mercy on you. He will return and gather you [from all the nations whither G-d, your G-d, has scattered you]. If your banished shall be at the utmost end of the heavens [G-d, your G-d, will gather you from there]… and G-d, your G-d, will bring you [to the land that your fathers possessed, and you will possess it]…”7
These words, explicitly stated in the Torah, include all the [Messianic] statements made by all the prophets.
There is reference [to this principle] also in the section of Bilam.8 There he prophesied about the two meshichim (anointed ones): the first anointed one who is [King] David who saved Israel from the hand of their oppressors; and the final anointed one [i.e., Mashiach] who will arise from [the former’s] descendants and save Israel in the end.9 Thus it says there:
“I see him, but not now”10 this refers to David;
“I behold him, but not nigh” this refers to the Messianic King.
“A star steps out from Jacob” this refers to David;
“and a scepter will arise from Israel” this refers to the Messianic King.
“He will smite the great ones of Moab” this refers to David, as it says, “He smote Moab and measured them with a rope;”11
“and break all the children of Seth” this refers to the Messianic King, of whom it is said, “His rule will be from sea to sea.”12
“Edom will be a possession”13 this refers to David, as it is said, “Edom became servants to David;14
“[and Seir] shall be a possession” this refers to the Messianic King, as it is said, “Saviors shall ascend Mount Zion [to judge the mount of Esau]…”15
2. In context of the “cities of refuge,” too, it says, “When G-d, your G-d, will expand your borders… you shall add three additional cities…”16 This has never yet taken place, and the Holy One, blessed is He, does not command anything in vain.17
As for the [other] prophets’ utterances [about Mashiach], there is no need for prooftexts as all the [prophets’] books are full of this concept.
3. Do not think that the Messianic King will have to perform signs and wonders and bring about novel things in the world, or resurrect the dead, and other such things. It is not so.18 This is seen from the fact that Rabbi Akiva was a great sage, of the sages of the Mishnah, and he was an armor-bearer of King Bar Koziba19 and said of him that he is the Messianic King: [R. Akiva] and all the wise men of his generation considered him to be the Messianic King until [Bar Koziba] was killed because of sins, and when he was killed they realized that he was not;20 but the sages had not asked him for any sign or wonder.
The essence of all this is that this Torah [of ours], its statutes and its laws, are forever and all eternity, and nothing is to be added to them or diminished from them.21
(Whoever adds or diminishes anything, or interprets the Torah to change the plain sense of the commandments, is surely an impostor, wicked, and a heretic.)22
4. If a king arises from the House of David23 who meditates on the Torah and occupies himself with the commandments like his ancestor David, in accordance with the written and oral Torah,24 and he will prevail upon all of Israel to walk in [the ways of the Torah] and strengthen its breaches,25 and he will fight the battles of G-d26 it may be assumed that he is Mashiach.27
If he did [these things] successfully (and defeated all the nations around him28), built the Sanctuary on its site29 and gathered the dispersed of Israel he is definitely Mashiach!30 He will [then] correct the entire world to serve G-d in unity, as it is said, “For then I will turn to the peoples a pure tongue that all shall call upon the Name of G-d and serve Him with one consent.”31
(If he did not succeed to that extent or was killed, it is clear that he is not the [Mashiach] promised by the Torah … for all the prophets said that Mashiach is the redeemer of Israel and their savior, and he gathers their dispersed and reinforces their commandments…)32
Chapter XII1. One is not to presume that anything of the ways of the world will be set aside in the Messianic era, or that there will be any innovation in the order of creation; rather, the world will continue according to its norms.33
As for that which is said in Isaiah, that “the wolf will dwell with the sheep and the leopard will lie down with the kid” 34 this is an allegory and metaphor. It means that Israel shall dwell securely alongside the wicked heathens who are likened to wolves and leopards, as it is said “a wolf from the plains ravages, a leopard lies in wait over their cities.”35 [In the Messianic era] all will return to the true religion and will neither steal nor destroy, but consume that which is permitted, in repose alongside Israel, as it is said, “the lion will eat straw like the ox.”36 All other such expressions are also allegories, and in the era of the Messianic King everyone will come to know what the allegory is about and what allusions are indicated.37
2. The sages said: “There is no difference between the present age and the Messianic era but [delivery from] subjection to foreign powers.”38
From the plain sense of the words of the prophets it is apparent that in the beginning of the Messianic era will occur the war of Gog and Magog;39 and that prior to the war of Gog and Magog a prophet will arise to correct Israel and to prepare their hearts, as it is said, “Behold, I am sending you the prophet Elijah [before the coming of the great and awesome day of G-d].”40 He will not come to declare the pure impure or the impure pure, nor to disqualify people presumed to be of legitimate lineage or to legitimize those presumed to be of disqualified lineage;41 but to establish peace in the world, as it is said, “He will turn the heart of the fathers to the children…”42
Some sages say that Elijah will come before the coming of Mashiach.43
All these and similar matters, however, man will not know how they will occur until they come to pass; for in the [statements of the] prophets these are undefined matters, and the sages, too, do not have a clear tradition on these subjects except for the [apparent] implications of the Scriptural verses. That is why they have differences of opinion in these matters. In any case, neither the sequence of these events nor their details are fundamental to the faith.
A person should not involve himself with the homiletical statements or protract on the Midrashim speaking of these or similar matters, nor is one to consider them fundamental; for they do not lead to either fear or love [of G-d].44
Likewise, one is not to calculate “ends” [dates of the Messianic redemption]. The sages said, “May the spirit expire of those who calculate the ‘ends.’ ”45 Rather, one is to await [the redemption] and believe the principle of this matter as we have explained.
3. In the era of the Messianic King, when his kingdom will be established and all of Israel will gather around him, all of them will have their pedigree determined by him,46 by means of the Holy Spirit that will rest upon him, as it is said, “He will sit as a refiner and purifier.”47 First he will purify the descendants of Levi,48 saying “This one is a legitimate Kohen (priest), and this one is a legitimate Levite,” while diverting those of improper lineage to the [rank of] Israelites.49 Thus it is said, “The governor [Nechemiah] said to them… until there will rise a Kohen with the Urim and Tumim;”50 from this you can infer that the determination of presumed pedigree and the public declaration of lineage is by means of the Holy Spirit.51
As for the Israelites, he will only determine their tribal lineage, that is, he will inform that “this one is of such-and-such a tribe and that one is of such-and-such a tribe.”52 He will not pronounce on those presumed to be of legitimate ancestry that “this one is a mamzer and that one is a ‘slave’;”53 for the law stipulates that once a family is intermixed [with the Jewish community at large] it remains intermixed.54
4. The sages and the prophets did not long for the Messianic era so that they may rule over the whole world or dominate the heathens, nor to be exalted by the nations, nor in order that they may eat, drink and be merry; but only to be free [for involvement] with the Torah and its wisdom, without anyone to oppress and disturb them, so that they may merit the life of the World-to-Come, as we explained in Hilchot Teshuvah.55
5. In that era there will be neither famine56 nor war,57 neither envy nor strife,58 because good will emanate in abundance and all delightful things will be accessible as dust.59 The one preoccupation of the entire world will be solely to know G-d. The Israelites, therefore, will be great sages and know the hidden matters,60 and they will attain knowledge of their Creator to the extent of human capacity, as it is said: “The earth shall be full with the knowledge of G-d as the waters cover the sea!”61
See the footnotes for actual references..
See also :
http://www.chabad.org/library/moshiach/article_cdo/aid/100903/jewish/Awaiting-Mashiach.htm