I recently started using a + in my email address to make use-specific aliases, so I can more easily filter content from them or see if they're leaking my email.

I signed up for a rewards program in person the other day and the strange look I got:

Do you have an account with us?

Idk

I can look up your email

Ok, it's foo@bar.com

I don't see it, would you like to make an account?

Yes, but instead of that email, make it foo+yourcompany@bar.com

Uhhhhh.... Ok....

Like "you don't have an account but you have an email specifically for our business? Sus AF"