I have little hope for a resolution of this.
The main fault lies with the provider of e-mail service (optonline.net, in this case, but they aren't the only ones who do things like this). A good e-mail service provider will allow the user to set up spam control to their own personal taste. These guys are blocking not only spammy IP addresses, but all nearby IP addresses as well. The goal is to coerce server owners into policing everything that happens on their servers.
The problem is, that can't possibly work. In our case, Jack leases two entire servers from Company A. Companies X, Y, and Z also lease entire servers from Company A, and operate them as shared servers, subleasing space to dozens of other companies and individuals. Some of those subleasors send out porn spam themselves, and some are innocents whose websites have been compromised by spammers and virus-spreaders. There is no way that Company A can police things all the way down to that level.
Add to this the fact that there are over 50 services that provide "blacklists" of spammy IP addresses -- and some of them are trying to profit by charging fees to "expedite" removal of addresses that are incorrectly blacklisted.
Anyway, this is not just a problem with Jack's e-mail, and it's not just a problem with optonline.net. Anyone who relies on e-mail needs to be aware that messages will not always be delivered, and it may be worth shopping around for an e-mail service provider that doesn't screw up your ability to communicate.
