Gmail address with "+" within the recipient name

Question

I've seen people list email addresses at Gmail with "+" within the recipient name.

Here's an example of what I mean:

[email protected]

That said, if you attempted to create a Gmail account with "+" recipient name, you would get this error message:

Please use only letters (a-z), numbers, and periods.

Is the "+" simply read and removed by the mail server, and if so, is this specific to Gmail, or is it universal to all email addresses/servers? Meaning my guess is that people to this for readability, but I've always been puzzled by it, since it appears to not be possible to create an Gmail account using a "+".

Answer 1

Plus sign is GMail's delimiter for aliases, which many people use for filtering and tracking spam.

For example, you want to make sure that your bank's emails are all legitimate so you'll register your email with the bank as [email protected] and then create a filter that deletes all emails that don't match from:MyBank AND to:[email protected]. Alternatively, when you register with a shady site you can provide your email as [email protected] and then create a filter to delete everything that is sent to that address.

However, beware that some sites have poorly-written validators on allowed addresses, which block emails with plus sign, which is actually an allowed character per RFC 5322. Google doesn't allow it simply because it's a reserved character in their system.

Answer 2

The plus sign is not simply a Gmail feature, but one of the valid characters in email addresses as specified by RFC-5233:

https://www.rfc-editor.org/rfc/rfc5233

It's true that many email validation tools don't take this into account. RFC3696 details techniques on how to properly validate email addresses:

https://www.rfc-editor.org/rfc/rfc3696

Of note is that the following characters are valid as long as they are not used to begin or end the local part of the address:

! # $ % & ' * + - / = ?  ^ _ ` . { | } ~

Answer 3

Google allows the user to use the plus sign and the period to make variations on their address

• The plus sign allows to to add any words you like after your base address
• the period lets you divide your name up anyway you want.

These are great for filtering your emails.

You are right that you can't have plus sign in your base address.

Answer 4

Adding the + sign to an email address is simply a variation of the same email address, just like the . in Gmail accounts.

The reason why people may use the + sign in their email address with Gmail is to filter their emails. In Gmail, you can filter emails based on who they're sent to, not just who they're sent from. Keeping this in mind, some people utilize this feature to prevent spam, or to better sort their inbox.

Source: I use Gmail, but there's also a help article on Google's website explaining this