AnonAddy.com is an anonymous email forwarding tool.
First, you create a username which is then used to create a subdomain such as “randomuser.johndoe.anonaddy.com”. If you don’t want the username revealed, you can also generate UUID aliases
You can then create aliases on the fly to use as email addresses when signing up at sites or for sending emails. The forwarding email address acts as a catchall so you can have an unlimited number of unique email addresses (I use something like this with another service so I can use a unique email address for every service).
Emails sent to any of those aliases get forwarded on to whatever email address you’ve designated.
The paid versions of AnonAddy.Com also allow users to set up custom domain names and additional usernames.