Well, except http://tools.ietf.org/html/rfc6854
I do not see anything in that doc that makes it valid to have a From
field with no domain name.
Section 2.1:
from = "From:" (mailbox-list / address-list) CRLF
In RFC 5322 sec 3.4:
address-list = (address *("," address)) / obs-addr-list
address = mailbox / group
group = display-name ":" [group-list] ";" [CFWS]
So this is valid:
From: Redacted for your own good :;
That's deliberate; the use case we had in mind is EAI mail downgraded
by a POP or IMAP server where there's no way to turn the EAI address
into an ASCII address.
R's,
John