This is just a quick note.
What I've found quite handy for testing in Web Development, it's having my own domain name and an email server.
I've set up email there in a way that all emails for any address in my domain are redirected to just one single email address - i.e "*@mikhno.org" goes to "[email protected]" (except for a few existing email addresses, which are excluded from this).
And thus, when I need to register somewhere to test something, I can easily use "[email protected]", "[email protected]", "[email protected]" and so on - and then check for emails in just one place.
It is very useful to test registration processes, email subscriptions, forms for gated content and a lot of other things where you need to provide a unique email address and be able to check the email.