Tony Finch writes:
On Tue, 27 Mar 2007, Arnt Gulbrandsen wrote:
2. I see quite a few addresses of the form 'localpart(_at_)hostname'. Say
between 1% and 1ppm of messages.
Yes, I see about 1 per 1000 on my MXs today. About 85% of them are @exe or
@dll so probably an artefact of one particular broken bit of ratware.
Well, really, .com, .exe, .dll, what's the difference? ;)
If 'localpart(_at_)tld' is guaranteed not to be valid, a smarthost's life
is simpler: 'localpart(_at_)something' is either a local address (not
subject to IETF rules) or invalid.
Private domains are not necessarily single-label, so your suggestion
isn't a general-purpose simplification and in fact probably *adds*
complexity: If your MTA can handle multi-label private domains
correctly then it should be able to handle single-label private
domains without any special cases.
Private arrangements _can_ be anything. In actual practice some are much
more common than others, and senders generating 'localpart(_at_)hostname' is
the one I would prefer not to fight.
Disclaimer: I'm not saying that 'localpart(_at_)hostname' is a good idea or
anything like that. I think it's a terrible idea and I wish people
would stop doing it. I'm only saying that if 2821bis keeps
'localpart(_at_)tld' invalid, 'localpart(_at_)hostname' will be less bothersome.