[Greylist-users] Re: Greylist implementation for diskless firewall appliances

[scott at spamwolf.com]

> 
> > One potential use of greylisting I've been thinking about
> > to implement it on a firewall appliance that has an SMTP
> > proxy. This enhances network security and reduces load
> > on mail servers from inbound spam.
> > Some questions for the list:
> > 
> > How large is the SQL database likely to get? Would
> > it be feasible to use a RAM based list without a proper
> > SQL database? Has anyone worked out a formula
> > for the size based on users/mail rate?
> 
> That depends on the number of users and the number of emails they get 
> from different people.  I think the best any one can tell you is that it 
> will get as big as it has to.
>

Well, I think I can do a little better than that;

One server I manage has 409 email addresses that have been using 
greylisting for over 30 days.  Currently, they have 151164 records.
The exact number varies with time, but not much after the first 3 days.
At 32 bytes per record, that's a little more than 4 megabytes.

So we can at least establish a lower bound of 1 megabyte per 100 users.
The upper bound is potentially unlimited, but practically speaking,
10 Megabytes per 100 users would be enough.

To achieve that, you need to hash the triplets, 
but that's not generally a problem.


Scott Nelson <scott at spamwolf.com>