Plus Addressing is a great way to quickly create custom (or disposable) email addresses based off your standard email address, by simply adding a "+" suffix string to an existing email address in Office 365.
For example, a plus address for firstname.lastname@example.org could be something like email@example.com that she could use to sign up for the newsletter at the Northwind web site. Then when Northwind sends a newsletter to firstname.lastname@example.org it will route directly to email@example.com. Kim could create an Inbox rule that then moves messages sent to this + address into the "Northwind" folder.
Plus addressing support in Office 365 is a great way to more easily manage your Inbox, and even track mail like marketing and sales campaigns