I think you are seeking the impossible.
Most ISP's have filtering software that REDUCES the amount of virus's that you receive. Indeed, during the last episode, many thousands of virus's were stopped, but the onus is on you to have up to date anti-virus software, that scans your e-mail as it comes in.
If you choose to enable heuristics within your scanning software, as yet unknown virus's may be trapped.
The bottom line is, it's sad to think that people that have the skill level required to write virus's, don't put their skill to better use!