Microsoft now allows you to create custom (or disposable) email addresses based off your standard email address with Plus Addressing. Add a unique “tag” to your email address to determine who shares your email address and to add more options for rules.
For example, ralphie@colorado.edu can use the Plus Addressing feature when signing up for Starbucks rewards as ralphie+starbucks@colorado.edu. If a spam email arrives from ralphie+starbucks@colorado.edu, Ralphie knows Starbucks shared her email address. Or a rule can be created when a message is received from ralphie+starbucks@colorado.edu for special processing.
You don’t need to do anything with your Microsoft account to start using this feature. Simply add a “+tag” after your username (can be first.last, alias) and before the “@” sign & emails will arrive in your inbox with the unique address.