[Mimedefang] perl expression to catch bad recipient addresses?

[Tony Nugent]

Has anyone got a perl expression that is failsafe to catch a badly
malformed recipient email address?  (ie, to check that an email
address is at least syntatically valid).

   I'm asking here because I really need something failsafe and
   watertight, legal characters, correct syntax etc.  eg, I assume
   that such a check would need to take into account if the
   recipient has an unqualified (ie, locally deliverable) address?

It is a relatively simple thing that I want to achieve... quarantine
and then discard any email that has a bad email recipient address.
These emails would bounce anyway, this would cut out that
unnecessary step.

  It would be nice to be able to remove only the bad/illegal
  recipient addresses from a list when there are multiple, but my
  understanding is that it is not possible to successfully re-write
  the recipient address list from the defang filter itself.

Viruses in particular are notorious for generating bad recipient
addresses (often containing 8-bit characters), sometimes dozens at a
time from a single source (we are an ISP).  Our preferred policy is
to allow the infected email through, but with the virus attachments
replaced with a warning -- but unfortunately they can generate a lot
of unnecessary mailer-daemon bounces.

Thanks.

Cheers
Tony