[dingaling]

> who's fault is it that I couldn't email you and let you know?

The user's fault; they are knowingly trading that risk for protection of their privacy. That says a lot for how they regard the service in question.

What about rejecting ISP-issued e-mail addresses? Those are also ephemeral, for those who use them.

What about Yahoo! / Outlook.com / Gmail addresses? in the vast majority of cases people using those have no 'hold' on them and their accounts can be suspended at whim.

Domain-related addresses can be lost if the registry decides to hike the domain prices beyond affordability, such as with the 1000% increase in Uniregistry gTLDs later this year.

Where to draw the line? All e-mail addresses are temporary.