If it’s truly a throwaway I just use an email address like shitsinthewoods@mailinator.com, grab what I need, and go on with my life. If I ever happen to need to login again, I’ll just send a password reset to the mailinator address and once again carry on with life.
There are a lot of services that disallow email addresses to services like mailinator. That's why I stopped using them, and instead, I have a special "garbage" address on my mailserver.
If it’s truly a throwaway I just use an email address like shitsinthewoods@mailinator.com, grab what I need, and go on with my life. If I ever happen to need to login again, I’ll just send a password reset to the mailinator address and once again carry on with life.