In the past I would have instinctively said 'mayb' simply because the spelling is similar to a lot of other words that would be pronounced in a similar way (e.g. made), but I've since learned that that's often not correct, so I've gotten into the habit of pronouncing words I'm unfamiliar with by breaking them up into syllables, as that's typically more likely to be correct... hence I'd now go with 'mah-beh'.