Because some services have sensitive information and need a reliable way to contact you. If you use my service and attach your credit card to pay for it, and used a disposable email to sign up with and your account gets breached, who's fault is it that I couldn't email you and let you know?

Sure if it's some throw away service that doesn't have such sensitive information, that's fine, but there's many reasons to use such a service.

> 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.

That makes sense, thanks. My line of thought was that if someone is using a disposable address they probably aren't going to respond to marketing anyways - they're just checking out your service.

Sometimes people use them for bots to create accounts.

Also makes sense. Thanks!