In email footer links to "manage preferences" or "unsubscribe," customer email addresses are being passed in a unsecured manner. Request is to create the ability to tokenize or encrypt customer data (email address) so that the subscription management links in email footers pass customer data securely.

Token should be unique.

Token should expire based on business need.

Token should not be reused.

Should be able to create multiple tokens for a single email address, that operate independently, so that multiple emails sent to a single email address do not share a token.

Base 64 is not secure enough for a solution.

Token should be randomly generated.

An API should be provided so that clients can communicate with the vendor and determine if the token is valid / not expired.