Receiving emails (MLS listings) from the listing agent

[Bienes Raices]

I've been approaching the listing agents (instead of using a buyer's agent) this time, with some success.

I've been finding the listings off of sites like "Realtor.com" and then calling the listing agent. The listing agent almost always tries to get me to sign up with them to receive MLS listings from their office via email. Does that put me under some kind of obligation to use the agent who sends me the emails as a buyer's agent if I find something I like?