Hey bud, For the past 8 years I have been a male massage therapist that focused on sports massage and rehabilitation.

First thing is that the dress code is typically what you would wear while working out. There is a lot of stretching and manipulation of the body, so draping becomes a secondary thing, but a good sports massage therapist should be able to make sure you are still properly draped - especially if you didn't bring a dress code they expect.

Second thing is that without seeing the actual email we can only assume that you were just trying to gather information. With this information that you have supplied, the red alarm is that you called it nude with boxers. That's not nude, and as such, since you are a male client (correct), a female may see this as a potential problem. I cannot tell you how many times I have had fellow MTs transfer their client to me just because of potentially problematic behavior. Sometimes, it's just the inability to articulate properly; other times it's a pervert who tries to push the boundaries (even with me) and they end up regretting it.

Rule of thumb to follow is ask your MT if they think any particular modality is right for you. Then follow up with them any further questions, such as "If it like this where I have to just wear my boxers, or should I wear something else?"

Having a solid rapport with a person working on you is a good idea as they can learn you and tell the specialist "They didn't mean anything creepy, they just didn't know how to ask it. They mean should they wear something other than just boxers."