> -----Original Message-----
> From: Ron McKeating [mailto:R.J.Mckeating@lboro.ac.uk]
> I really like the sound of the callout option, but it scares
> me, will it
> break things for lots of users if I switch it on ?
It depends on the sites you get mail from. The default timeout is 30
seconds, which is too short. Sites that take longer than this to respond,
for whatever reason, won't be able to send you mail. The timeout is
configurable; 1 or 2 minutes is probably a good value. You may want to set
up your ACL so you can put in a list of sites that you don't want to do
callouts for, so you can whitelist any problem sites you need to get mail
from.
It's also a slightly controversial thing to do because it can consume
resources on unrelated sites. If somebody spoofs a bunch of mail with
example.com as the return address, suddenly example.com has to deal with
responding to callouts for mail it never sent.
It's undeniably a very effective anti-spam technique, though.
