Using Email Subaddressing to Track and Filter Your Inbox
Creating and understanding email Subaddressing. Notice who has shared your email address and learn a method to manage your inbox.
Subaddressing (or "plus addressing") is a powerful feature for organizing incoming email supported by many major providers. Originally a hallmark of Gmail, it is now available on Microsoft Outlook (though it may require administrative activation for business accounts), Yahoo, and Proton Mail—where it is referred to as +Aliases.
By using subaddresses, you can effortlessly filter, label, or sort incoming mail using automated rules.
How It Works
Suppose your primary email is Obfuscation@PsyberSec.io. If you want to subscribe to a newsletter on a site like KrebsonSecurity, you could provide the address Obfuscation+krebsonsecurity@PsyberSec.io.
Regardless of which internal system the sender uses, the email will arrive in your primary inbox. Because of the unique "+tag," you can create a rule that automatically labels these emails or moves them to a specific folder. You can use any label—for example, +meals for food-related subscriptions.
The Technical Risks
While subaddressing is excellent for newsletters, I do not recommend using it for account logins. Not all web platforms handle special characters gracefully. For instance, I once registered for a major retail site using a subaddress. While it initially worked across their web and mobile apps, a subsequent code update on their end broke the login logic. Because their system no longer recognized the "+" as a valid character, I was locked out and had to open a support ticket to have the address manually changed.
Limitations
Can you reply to an email as Obfuscation+krebsonsecurity@Psybersec.io? Genuinely, no, but some email services use your subaddressing email on your replies. Subaddressing is designed for receiving mail. There is no list of +tag that you may managed in an email provider natively.
Privacy Benefits
Using Subaddresses reveals how your data is shared. If you start receiving spam at an address specifically created for one service, you know exactly who leaked or sold your information. While it doesn't hide your primary email, it provides a layer of privacy that allows you to direct unwanted traffic straight to your spam folder.
Subaddressing is a "zero-setup" tool that requires no new accounts. While dedicated email aliases offer higher privacy, subaddressing is the perfect starting point for better inbox control.
Want to have some fun? Send a friend an email using +tag, username+message@domain.com and see if they spot the hidden note!