As you probably know, Mailinator has a always-growing list of alternate domains. However, those are just the domains sponsored by us.
In truth - Mailinator accepts ANY email you fling at it*. In other words - you can setup your OWN personal domains simply by setting your MX record (i.e. through your registrar or DNS server) to point your mail delivery to Mailinator!
Simply put - if you own YOURDOMAIN.com, you can simply change that domain's MX record to point to mail.mailinator.com and all email you send to @YOURDOMAIN.com will then end up in Mailnator.
You can publicize this fact - or you can keep your personal alternate domain a secret and have your own private Mailinator !
*pursuant to normal draconian Mailinator email rejection criteria including but not limited to hate email, unlawful email, etc.