Well... Use SME Server 6.0.1-01 to start with.
Sorry, that's what I've been using. I wasn't clear.
Then beofore installing anything else, make sure the box works like you want.
Depending on your meaning of "like you want" I do; I check that it behaves as I expect, at least, but as my main motivation at the moment for using SME is to catch spam and email viruses I need some contribs to do this.
Then check the contribs.org documentation feedback pages on the various contribs and how-to's BEFORE installing it/them.
Again, this is something I have done. Often I see others with similar problems but no resolution, which on a project as well established as SME I tend to assume means that the problem clearly isn't very common. For example, I bounced several hundred email on one occassion with the same problem as
here. Given the prominence of spam and virus checking, I'm sure that many people are getting it to work without problem.
Next to that, why not set up a test box and do a test run after installation of EACH contrib before you continue.
I should have made it clearer that I've been playing with SME/E-Smith for years, starting with 4.x. With 6.x, and in particular 6.0.1-01, I've built and rebuilt several times with minor changes to the approach and wildly varying results, hence this question; what is a good starting point to get an anti-spam/virus SME server; I plan to use this as a starting point for several experiments with contribs from various sources.
Perhaps my assumption that a large proportion of SME users have their own base installation method (install this ISO, then this contrib and these updates, etc) was wrong.
NB: It would perhaps have made more sense to post here with specific problems rather than where I did start; I would have done so but I only had read access to the forums when I went through a week of hell a week or so ago when I tried so many minor variations on a basic theme and seemed always to gain something only at the expense of something else, and lost hundreds of emails in the processs (mostly a mixture of spam and mailing list emails, but frustrating all the same). So when I got forum access I thought I'd start by trying to "steal" someone-else's setup

I would also stress how important it is to have good AND compatible hardware.
Good point, and one I hadn't thought of. I'm 99% sure my problems are configuration not hardware but I'll do some research on this all the same.