ISP blocking of email from open email relays

In 2004, there were press stories about the discussion in online message boards about Verizon's decision to block all email routed through open email relays. Open email relays are susceptible to abuse by spammers who are looking for a way to distribute email.

Someone claiming to work for Verizon in their tech support area stated as follows:

"Apparently, Verizon is blocking email coming from open relay mail servers. Essentially, this means that all email coming from servers that don't have an authentication process are being blocked. Open relay mail servers are typically hotbeds for spammers, as no authentication is necessary. Unfortunately, many email servers in Europe (and the rest of the world for that matter) are open relay. This is yet another brilliant idea that some idiot who doesn't know jack about computers making decisions for the company. I expect this to blow up in their faces sooner rather than later."

Consider also this statement of policy from a Montana ISP, Montana Network, LLC. The policy lists several domains the ISP blocks email from. Consider the impact of these policies on the commercial use of email.