As far as I know, it does. ASSP greylisting is a bit of a mystery to
me, though, to be honest, so this aspect you should research. I don't
think it is using greylisting in the same way as XMail does but I am not
really certain (there is some sort of a greylist download that occurs
and is used, rather than the refuse/send mechanism that is the kind of
greylisting XMail uses).
As far as I know all of the scanning takes place during the SMTP
session, as I mentioned - 15K (or whatever you specify - many users
swear by just using 5k) is allowed through then the Bayesian filter
makes a determination. I am pretty certain that the greylisting
mechanism is actually invoked prior to this, so it is more or less the
first thing that happens. There is also SPF checking, RBL checking,
proper header construct verification, verification against an LDAP
lookup (if desired) and other stuff.
After training ASSP, users have the option to receive SPAM marked (which
I discourage since the entire mail has to be dealt with then, which is
inefficient) or to have it refused, or to not have it scanned at all if
outside corporate policy on that. Because the whitelisting mechanism is
so robust, and the Bayesian filter quite solid, I have had almost no
complaints about false positives. I presently have about 4000 emails go
through a day with something like 90 users, all remote - I provide
filtering for a small corporation and operate as a web/email host as
well. Inevitably with this number of users some people want mail from
Costco and some people don't, so there is no perfect solution.
Jeff
John Kielkopf wrote:
>Jeff Buehler wrote:
>
>
>
>>I simply disallow email of greater than 5 mb (that was my cutoff
>>exactly!) - email is not ideal for large file transfers for a number of
>>reasons, so I discourage it.
>>
>>
>>
>>
>I agree, however some of my users may say otherwise ;)
>
>I was thinking about scanning all messages <2MB durring the SMTP
>session, and then scanning the few larger ones off-line at low
>priority. Currently I just don't scan anything > 5MB.
>
>
>
>>The accuracy I
>>have had once properly configured is exceptional (98-99%) - in ASSP
>>whitelisting is very important and automated which helps a lot. I
>>prefer it over Spam Assassin myself.
>>
>>
>>
>>
>Do you get many complaints about false positives? Roughly how many
>users do you have?
>
>I prefer to do most of my antispam in the SMTP envelope, before the DATA
>phase. It's just a waste of bandwidth otherwise. Do you know if
>greylisting in ASSP does this?
>
>Thanks,
>--John
>
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