"may certainly" is correct and usable in written English.
You can use it to express an affirmative answer or agreement to an idea. For example: "If we work hard, we may certainly succeed."
But Putin may certainly try.
May certainly has advice on hand.
In commercial terms, then, such research may certainly have hit a rich vein.
You may certainly ask for mashed potatoes or broccoli or fries.
The investigation may certainly have been unprofessional, and deserves the scrutiny it will no doubt receive.
It may certainly prove more scintillating than what appears to be the election's litigious endgame.
With your general guest list, you may certainly set the overall tone and feeling for your wedding.
It may certainly be said that puppet theatre has everywhere antedated written drama and, indeed, writing of any kind.
One may certainly take issue with Nikitin's characterization of these feminist activists and conceptual political artists as violent anarchist revolutionaries.
ARTLB, Canada Dr. Huang responds: Other individuals with Asperger syndrome may certainly share the difficulties you report in your son.
That may certainly may be so, but any abuse has little to do with a cable company's size.
