If your provider is working for you, then all is good. I suspect they either A) have hundreds of thousands or more e-mail users in total, or B) they work through one of the big providers for you.

If your provider only serves 20,000 or fewer e-mail clients, the costs for them to independently play white-list, black-list, whack-a-mole, pleading to keep their legitimate users' e-mail working smoothly would be prohibitive - upwards of $10 per year per e-mail account just for the employee(s) tasked with negotiating (and solving) those issues behind the scenes for their users (including you), not to mention policing their users to prevent them from abusing the e-mail system.

It's basically a problem of prejudice - if any e-mail account remotely linkable to yours by any metric mis-behaves, some admin somewhere will block it along with anything remotely associated with it - including your e-mail service. Then it's up to you, or your organization, or your organization's service provider, to track down the offended party and somehow negotiate with them to restore the blocked services for the innocent users.