One thing I learned operating a payment processor for a decade is that by far the email domains of choice for people trying to do evil were big free email provi

One thing I learned operating a payment processor for a decade is that by far the email domains of choice for people trying to do evil were big free email providers like google, ms, yahoo and so on. A few operators would use something like mailinator (the kind of thing that is being blocked here). By evil I mean everything from attempting to hack us and our users, to financial fraud, to just trying to get a merchant account after being blacklisted by Visa. A lot of the logic I see in replies here is that people use services like mailinator to abuse free trials. I think this is also the logic for blocking or stripping RFC 2822 email addresses (something+somethingelse@gmail.com). On the RFC 2822 stripping / blocking, you are just breaking the internet. Disposable emails seem like a problem, but I suspect the trend is towards more "private" email forwarders like Mozilla's relay, Indeed's private emails and iCloud's hide my email. If you are having problems with free tier abuse, one small thought... This isn't universally applicable advice... but it may be helpful. If having an account on your service does not accrete value for the user, the user will be ok with abandoning the account and starting from scratch to get free service. If it is not possible to accrete value, you may have a product that is not a good fit for the freemium model. Try alternative models. You may find you are leaving money on the table.