Email Plus Addressing, also known as sub-addressing or tagged addressing, is a feature that allows users to create variations of their primary email address by adding a "+tag" or "+keyword" after their username but before the "@" symbol. For example, if your email address is "username@example.com" you can use "username+tag@example.com" or "username+keyword@example.com" to create unique email addresses that still direct emails to your primary inbox.

This feature is beneficial for organizing and filtering incoming emails. Users can set up filters or rules based on the "+tag" or "+keyword" to automatically sort emails into specific folders, label them, or apply other actions. It also helps users identify the source of incoming emails more easily, as the added tags or keywords can indicate where the email address was shared or used.

Overall, Email Plus Addressing provides a flexible and efficient way for users to manage and organize their emails without the need to create multiple email accounts.