On Sat, Sep 04, 2004 at 10:45:44AM -0600, Ryan Thompson wrote: > Yep. Good idea, overall. There are a few gotchas: > > TLD extensions sometimes map file extensions. We might have to whitelist > command.com, and the entire country of Poland. :-) > > Since the domain is in plain text and doesn't contain a protocol or > subdomain (i.e., 'www'), I haven't yet seen a mail client that will > display it as a clickable URL.
This is generally the tact we're taking in SpamAssassin -- if a general
MUA doesn't display it as a link, then we don't consider it an URL.
Another issue for the generic domains thing is performance -- lots of
messages have lots of things like could potentially look like a domain,
and querying for them all adds a bit of a load on the client and the
server.
For instance: /\b([a-zA-Z0-9_.-]{1,256}\.[a-zA-Z]{2,6})\b/
in theory (I haven't tested it), will grab anything that looks like a
generic domain name in text. If you check that list against a list of
valid TLDs, you'd probably end up with a decent list, but you'd hit the top
issue quoted above where "Go take a look at command.com" isn't clear if it's
an URL or a filename.
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