Looking on the internet deeply has found these results:

what can i do for you is the most popular phrase on the web.

what may i do for you 1331,000 results on the web	what can i do for you 1621,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
What may I do for you, sir? What may i do for you today, sir? What may I do for you, Ms. Groves?	What can I do for you tonight? Now... what can I do for you this afternoon? What can I do for you Madame President What can I do for you? elect? In Brooklyn, a dry cleaner. What can I do for you?

what may i do for you

1331,000 results on the web

what can i do for you

1621,000 results on the web

More popular!