Also sprach Philip Ronan:
I suppose that's because there's no point in having valid domain names
defined in multiple documents.
That makes sense, but then why not a simple reference to the RFC defining
domain names?
A valid email address should conform to both.
So I must combine all the different specs and use the "greatest common
denominator"?
OK, I'm not that familiar with RFC1034/1035, but I assume they only
relate to the part of an email address that comes after the "@". A
dot would be essential because there are no web domains that consist
of a single TLD (like "com" or "uk").
What about "localhost"? But it seems, that RFC2821 is contradictory within
itself. Section 2.3.5 says: "A domain (or domain name) consists of one or
more dot-separated components." Thus, "my-domain" would be valid. But - same
RFC(!) - section 4.1.2 defines
Domain = (sub-domain 1*("." sub-domain)) / address-literal
In other words, at least one dot is required. Which section am I to believe?
AFAIK, there is no limit on the length of the part before the "@"
RFC2821, section 4.5.3.1 says there is a limit of 64 characters. But then, I
think it is RFC1035 which explains that mail addresses are converted to
domain names by making the part before the @ another "subdomain", and
because of the way such a domain name is encoded, the limit should be 63
characters (not counting quotes or escape-backslashes). So, again, what am I
to believe? It's all so confusing :-(