a) No, because email is the product in of itself. If you had to have an email account, login into your email account through a client, and then access something else that requires the previous two then I would say in that instance that it is DRM. In that case the email client would be the source of the DRM, not the email it gives you.
b) If you are required to have an account for a piece of software that controls your access to other software, be it to use or just download, then yes I see that as a form of rights management. To use my own analogy, I can burn my own DVD with no DRM and play it on my DVD player, but the DRM is still required to play commercial discs; therefore the DRM still exists even though I have an opportunity to not be encumbered by it. Or here's another thought, if someone's account on Steam was revoked, can they still use that account to download the free-to-play games that have no DRM? Granted, they could just create another free account, but still...
With b) it's as I said, I understand your view and you certainly need your account for that one time when you buy the game. So if your account gets closed at a later time you still have full access to the game. But that would make Amazon.com DRM as well as you can't buy your game without having an Amazon account.
In that case, yes I view Amazon as a form of rights management. On their system you are allowed to purchase and take delivery of said game, after that it no longer manages anything anymore.
But I don't think you understand my view. Just because a rights management system lets you do something without encumbering you doesn't suddenly mean it isn't a rights management system.
Your view seems to be that in a few situations Steam operates as a delivery service for a free game that Steam does not restrict you in any way beyond that, therefore it is not a rights management system. My view is that it is because the rights management is clearly in the system, it's just up to the developer to use it or not.
It's even conceivable that Valve could restrict a person's account from downloading a free-to-play game for whatever reason they desire.
The downloading of a free game is the simplest form of rights management it has, it lets you download the game with your account. But in many, if not almost all, other instances it manages your rights based on the criteria of the system and developer.
Steam is DRM, but it was created to balance out the needs of the consumer and producer that hopefully benefits both. Just because most forms of DRM seem to be created to only benefit the producer and not the consumer doesn't make DRM a horrible thing. Therefore, it doesn't seem right to try to explain something like Steam, that can behave as DRM, in a way that makes it seem like it isn't DRM.
By the way, I've enjoyed the discussion, it's given me new things to consider in my viewpoint on DRM and Steam.
Okay, I'll answer for two cases as I'm not sure I understood you correctly. You probably mean b) but still:
a) That would mean E-Mail is DRM as an account is needed.
b) So whenever an Account is required to download something it's DRM? I can understand that view though I do not share it.