Temporary disposable email addresses

My users want to be able to use temporary email addresses, that do not show the real email address, but nevertheless will deliver email correctly.

There are many types / examples of this around the web, but I don't use one specifically to use as an example.

My understanding is that one can enter an address with a "core" known piece, and postfix (or infix) random pieces. This resulting email address will be unique, and map to a hidden email address on the server.

Example: I have a real email address called "fred". I set up a "mapping" (alias) as a disposable email address of "peter", and perhaps an expiration cycle of 2 days (after which a temporary address is retired).

When I go to a new site, I give them the email address "peter_virtualminnewsletter@mydomain.com" and I can see if any spam comes to that email address. The variable portion of the email address should allow large enough text for some description so that people would recall what the email address was used for. I don't know the email specifications for max allowed length...