ISP typically take the way too aggressive approach as Verizon seems to be doing. This certainly doesn't surprise me.

From this article:

Since mid-December, users have complained on Internet message boards and to Verizon customer service centers that they are not receiving legitimate inbound e-mail from Europe and Asia. Verizon, they say, has taken the unusual step of blocking nearly all mail from certain geographic areas because some networks in those regions are used by spammers.

At SimpleFilter the decision to block email that is either low, medium or high probably of being spam is entirely up to the customer.

I have to admit that we've been tempted to globally block all mail from Asia but we have other measures in place to deal with it efficiently.