Mail filtering and forwarding

I have a domain, call it A, which is stuck on dialup. It gets about 600K (!) emails a day, 599K of which are pure spam to accounts which don't exist, such as bill123.

A different computer, call it B, acts as primary MX for A, directing all non-account messages to the bit bucket and forwarding the remaining 1000 messages to A over dialup. Most of these are also spam, but both I and dialup can deal with them easily enough.

B is a 5 year old machine running qmail, used for some other purposes as long as it is around, but filtering and forwarding are the only real reasons for its continued existence. A friend told me about Linode and it seems tailor made for replacing B, which is getting a bit long in the tooth, especially for a laptop.

This mail filtering could be handled by a simple regex on the RCPT TO: envelope recipient (^(postmaster|root|webmaster|account1|account2)), but for various reasons, it is currently handled by a Perl program invoked by qmail's dot-forward process. It usually has a load factor of around .4. That would certainly drop on a modern machine with a proper qmail install which didn't need to invoke Perl on every message, even though I used PersistentPerl to speed things up. Storage is minimal except when I bork A and it takes a day or two for my poor sysadmin skills to recover.

So, several questions.

1. Is this a good fit for a Linode 360 running slackware or gentoo? No X, no rdbms, no apache, just a mail server and ssh, maybe djbdns.

2. I originally migrated to qmail years ago when it was that or sendmail and I got tired of all the sendmail security holes. I like many things about qmail, but I do not like the proliferation of patches, and especially the confusing conflicting combined patches. I have thought about switching to postfix but don't have a spare machine to play with. Does anyone with experience with both have any comments? Is this filtering, a regex on the RCPT TO: envelope recipient and nothing else, enough enough to do in postfix? How about the forwarding from B to A? It's been ages since I actually did much to qmail, and I have never done more than skim documents, so I would be basically starting from scratch.

3. I see many references to "dedicated IP addresses". Is this Linode-speak for static IP addresses? I don't want a dynamic address for A's primary MX provider; even if the DHCP server and DNS are tightly integrated and switch together,, there is still the matter of other machines using the cached old incorrect IP address for an hour or two after. If static IP addresses are available but not standard, how much do they cost?

4. When I set up a machine myself, I always keep it offline until I have set up the firewall and services. How does this work under Linode?

The very concept of Linode tickles my brain, and I can see lots of ways to experiment for only $20 a month. Heck, the first thing I might try would be a secondary MX at a different data center. The possibilities are endless.