A user with the email address of firstname.lastname@example.org can use the plus addressing feature to extend their email
address to email@example.com and all emails sent to the firstname.lastname@example.org email will land in the
user's email@example.com inbox.
The "tag" can be unique, allowing users to generate an infinite amount of custom email addresses, which they can give out to companies in newsletter sign-up forms, contact forms, and other online forms. Once emails arrive in the user's inbox, the owner can see where the email came from by the email address the sender used.
Now the user that subscribed to my newsletter can now easily distinguish my newsletter emails and there are many advantages for doing this.
This feature is also available with Microsoft's outlook.com and hotmail.com email services