> Could use + in the first part of email [...] email service, who respect the rfc, will threat them as the same.
I'm not aware of any RFC that says that mail sent to a+foo@example.com should go to the same mailbox as mail sent to a+bar@example.com (nor am I aware of any RFC that forbids this). I thought that GMail made up that feature and other vendors followed suit since users find it handy.
> Subaddressing is the practice of augmenting the local-part of an
> [RFC2822] address with some 'detail' information in order to give
> some extra meaning to that address. One common way of encoding
> 'detail' information into the local-part is to add a 'separator
> character sequence', such as "+", to form a boundary between the
^^^^^^^^^^^
> 'user' (original local-part) and 'detail' sub-parts of the address,
> much like the "@" character forms the boundary between the local-part
> and domain.
(Highlighting by me)
The RFC even gives an example using the hash:
> o A message addressed to "5551212#123@example.com" is delivered to
the voice mailbox number "123" at phone number "5551212".
I'm not aware of any RFC that says that mail sent to a+foo@example.com should go to the same mailbox as mail sent to a+bar@example.com (nor am I aware of any RFC that forbids this). I thought that GMail made up that feature and other vendors followed suit since users find it handy.