Note that RFC5233 doesn't actually standardize the delimiter. It uses "+" "#" and "--" in examples.
All RFC5233 does is specify how sieve (a protocol for specifying server-side email filters) can describe filtering on subaddresses. It does not confer any actual interpretation on email addresses, especially since many email providers don't actually use sieve for their email filters.
All RFC5233 does is specify how sieve (a protocol for specifying server-side email filters) can describe filtering on subaddresses. It does not confer any actual interpretation on email addresses, especially since many email providers don't actually use sieve for their email filters.