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 [email protected] denotes the same delivery address as [email protected] RFC 5233,[15] refers to this convention as sub-addressing, but it is also known as plus addressing, tagged addressing or mail extensions.

For any business user or organization today, the decision to use email is a no-brainer. Business simply can't be done in many cases without it. But that doesn't mean you can interchange email platforms or service providers at will. Digging into the capabilities of these services reveals a great deal of additional feature scaffolding that surrounds almost every email implementation by necessity.
The format of email addresses is [email protected] where the local part may be up to 64 octets long and the domain may have a maximum of 255 octets.[4] The formal definitions are in RFC 5322 (sections 3.2.3 and 3.4.1) and RFC 5321—with a more readable form given in the informational RFC 3696[5] and the associated errata. Note that unlike the syntax of RFC 1034,[6] and RFC 1035[7] there is no trailing period in the domain name.
I find it really annoying that people who used to check their email regularly, now leave large intervals between accessing their messages. This seems to be a social media thing where they’re all busy putting up their lunch pictures etc. etc. up for ‘everyone’ to see. Unfortunately this behaviour seems to be spilling over to the less conscientious in their work activities and they seem to be treating digital mail with contempt in some cases. Guess it’s back to paper mail and ‘snail’ delivery – not that that always gets the attention it deserves.