At 10:33 AM 4/11/2008, you wrote:
I gave up sending abuse reports to Yahoo (and Hotmail) many years ago.
I gave up on Hotmail, too, though occasionally I try a sample to see if they've improved. The latest came back with a message saying that I had to resubmit my report to any entirely different address. As if their inability to forward mail internally is now my problem...
So in the short term, advising customers that Yahoo's and Hotmail's freemail services are of very poor quality and should never be relied on for anything, and that Gmail is a better choice, is probably viable. In the long term, though, I think it may only delay the inevitable.
OTOH, as someone who provides services to small business customers who want their own domains, this may be to my benefit: one of the main selling points of a domain is that it makes you the master of your own fate, not tied to the fate of a particular provider. (At least, if you're smart enough to use a registrar and a service provider who doesn't make it almost-impossible to switch....)