Are Signup from Email Addresses with Plus Addressing Blocked?

What is plus addressing?

Also known as  subaddressing, tagged addressing, task-specific addressing or mail extensions, plus addressing is a way to dynamically create recipient addresses using an existing email address by utilizing the plus sign (+). 

An SMTP email address uses the basic syntax <user>@<domain> (e.g. 

Plus addressing uses the syntax <user>+<tag>@<domain> (e.g. 

In this method, the original email address must be valid for it to work in the first place. The +tag value that you add is arbitrary, although regular character restrictions for SMTP email addresses apply (for example, no spaces). 

If you don’t want to create multiple accounts or aliases for specific tasks, just add a plus sign (+) and any word before the @ sign in your current address. Messages will still reach you, and you’ll have an infinite amount of emails for different purposes.

Prefinery doesn't block signups using this method

Prefinery doesn't block signups from email addresses with plus addressing, because it's still a legit email address. Lots of people want to use it for labeling in their email client by filtering these addresses by the +tag

For example, if your email address is, you can: 

  • Sign up for newsletters with
  • Join referral programs using
  • Let clients and customers contact you through
  • Allow your team to forward urgent issues in your inbox via

Prefinery doesn't record referrals using this method

While they aren't blocked when used to sign up, Prefinery does detect referrals using plus address variations of the same email as the referrer's and blocks those referrals. 

The result is those signups will be allowed, but no referral will be created. The referring user will not be credited with a referral, will not move up the waitlist/leaderboard, and will not earn rewards. 

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