He is called the "seal of the prophets" by Islamic text. This should be a red flag immediately. No Jews or Christians call him the seal of the prophets. And with good reason. The Jews sealed all main scripture shortly before the fall of the Temple. Curiously, they sealed their scripture right around the time of Jesus. Almost as though they are deliberately trying to sweep a certain figure under the rug.
The Romans certainly were. But yes, Jews kinda write around the existence of Jesus, using their rabbis to make excuses why he cannot be the Messiah.
Nevertheless, there is ample historical evidence from a number of sources, not only Christian but also those opposed to Christianity, much of which was only a few years from the event of Christ's crucifixion. And while some of it misunderstands Christianity (in some sources, they are compared to vampires), it is overall real history. Alexa calls Jesus a mythical figure, and Muhammad a historical one. Turns out she got it backwards.
Outside of the Quran, no evidence for Muhammad's existence appears for nearly three centuries. Btw, Mecca? It didn't exist when Muhammad was supposed to have lived in it.
Now, as for the "seal of the prophets," Jesus sealed the prophets when he said:
For false Christs and false prophets will appear and perform great signs and wonders that would deceive even the elect, if that were possible.
Jesus warned that many would come after him, but the point he was making was that the law had already been fulfilled with him, so these later teachings were just so much rubbish. I reject Revelation, just as I reject Nostradamus, just as I reject Muhammad, or I reject Joseph Smith. Or Bahaullah (I think that's how his name is spelled). Whether the prophecy is good, bad, or indifferent, from now on, while scripture may be interpreted, no more prophets have come.
This is why Islam is not true. Because it relies on the false teachings of a power-hungry camel trader instead of the word of God. And the word of God is that you don't need prophets any more. Christ died on the cross to give you perfect freedom. Don't squander it by believing cult leaders who want your money and your happiness.