The intro starts with a I - vi - ii - V progression in the 1st two bars and then utilizes a iii minor substitute chord for the C major7 as it restates the intro in the 3rd and 4th bars (note that Cmaj7 is spelled C - E - G - B and E mi7 is spelled E - G - B - D).

The 1st half of the verse is in the key of C, except for the Bb maj7, but even it sounds more like a D mi7 (ii chord of C) with the A note on top. D mi7 is spelled D - F - A - C and Bb maj7 is spelled Bb - D - F - A.

The 2nd half of the verse is easiest to think of as modulating keys. The F major in bars 9 and 10 sounds natural as the IV chord to the key of C. The F minor in bars 11 and 12 is a real switch and could be viewed several ways, as the ii of Eb, or the iii of Db, or the vi of Ab. If the latter is chosen, the Db lydian mode slides smoothly into D ionian in the upcoming ii - V in bars 13 and 14. The last 2 bars are another ii - V in the key of C. The graphic below states some scale possibilities.