Gmail offers the ability to append a plus sign (+) and a string after the username and before the at sign (@) in your email address and still receive emails to that address in your main inbox.
For example, if your email address was email@example.com, you could sign up for a newsletter using firstname.lastname@example.org and still receive the email newsletter in your regular inbox. This capability would let you filter messages based on the email address it was sent to.
Unfortunately, plus signs are not permitted in the email address you use to sign up for Cloud Academy. If you try to sign up a Gmail address that includes a plus sign, you will see this error.
To fix this error, please use your normal personal or business email address to sign up.