Some mail services support a tag included in the local-part, such that the address is an alias to a prefix of the local part. For example, the address joeuser+tag@example.com denotes the same delivery address as joeuser@example.com. RFC 5233, refers to this convention as sub-addressing, but it is also known as plus addressing or tagged addressing.

https://en.wikipedia.org/wiki/Email_address#Subaddressing

by: Martin S. | over a year ago | Mailbox Management