Quick question on RFC2822. Sect. 3.4.1 on address formats states:
3.4.1. Addr-spec specification
An addr-spec is a specific Internet identifier that contains a
locally interpreted string followed by the at-sign character ("@",
ASCII value 64) followed by an Internet domain. The locally
interpreted string is either a quoted-string or a dot-atom. If the
string can be represented as a dot-atom (that is, it contains no
characters other than atext characters or "." surrounded by atext
characters), then the dot-atom form SHOULD be used and the
quoted-string form SHOULD NOT be used. Comments and folding white
space SHOULD NOT be used around the "@" in the addr-spec.
To me, this means that the local-part of an address may either be
quoted or may contain dot-atoms, but may not contain embedded quoted
substrings.
Correct. Addresses with multiple quoted strings in the local part have proved
to be both useless and an operational nightmare so they are no longer
considered to be valid.
For example, consider the following address local-parts:
VALID: vince.sabio
Yes.
VALID: "vince sabio" (deprecated, but nonetheless valid)
This is valid. But while it may not be an especially good idea to use such
address formats, section 3.4.1 doesn't deprecate them. What's valid but
deprecated is:
"vince.sabio"
NOT VALID: vince."human mail server".sabio
Yes, this is no longer valid. (Thank goodness.)
Ned