Reading RFC 822 again, I spotted the endorsement for the case at hand.
The named header is compliant to the standard, as quoted below.
However, the same standard does not compel a server to accept e-mail
sent to undisclosed recipients: we are free to reject it by local policy.
6.2.6. MULTIPLE MAILBOXES
[...]
A set of individuals may wish to receive mail as a single unit
(i.e., a distribution list). The <group> construct permits
specification of such a list. Recipient mailboxes are speci-
fied within the bracketed part (":" - ";"). A copy of the
transmitted message is to be sent to each mailbox listed.
This standard does not permit recursive specification of
groups within groups.
> While a list must be named, it is not required that the con-
> tents of the list be included. In this case, the <address>
> serves only as an indication of group distribution and would
> appear in the form:
>
> name:;
Some mail services may provide a group-list distribution
facility, accepting a single mailbox reference, expanding it
to the full distribution list, and relaying the mail to the
list's members. This standard provides no additional syntax
for indicating such a service. Using the <group> address
alternative, while listing one mailbox in it, can mean either
that the mailbox reference will be expanded to a list or that
there is a group with one member.
A. EXAMPLES
A.1.5. Address Lists
Gourmets: Pompous Person <WhoZiWhatZit@Cordon-Bleu>, Childs@WGBH.Boston,
Galloping gour...@ant.down-Under (Australian National Television),
Cheapie@Discount-Liquors;,
Cruisers: Port@Portugal, Jones@SEA;,
Another@Somewhere.SomeOrg
