Thanks foxb. I am going to be sharing this server with one other user. We maybe send out ten messages a day each and the amount we receive will vary but never anything that dramatic. I was under the impression that qmail is extremely robust, however in Kloxo we just can't get it to work at the moment despite the best efforts of my server manager who has 8 years of experience in installing various systems. In testing, while we set this up, the server is rejecting every single message. I believe it could be a glitch in the 64 bit version and we could drop down to the 32 bit version but it seems like an awful waste of that 8 gigs of ram.
The interface in ispCP looks really good and is perhaps the best I have seen. The server I am moving away from has WHM/cPanel and despite all the hype surrounding cPanel I've never really liked it or at least when working at root level and it has been costing me €29 euros a month.
I wonder does ispCP provide shell access for users? It's not something I would use myself but the other user would like to have it and Kloxo does allow that. Indeed there are many aspects of Kloxo that we really like, however we started this install last Saturday and it's still not finished because of this email nightmare. I even suggested we try using the Google MX settings to bypass the Kloxo system, but I haven't heard back on that suggestion so far.
Although the new server currently has Centos installed there is no reason why we can't install Debian or some other OS if that would work better with ispCP. I went for Centos initially because my old server uses that and it has always been very reliable.
Any thoughts or suggestions would be welcome. We are just looking for something that is simple to use, fast, stable and obviously secure when properly setup.
I've just been doing some research on postfix v qmail
http://shearer.org/MTA_Comparison and while qmail has some good points it does seem as though it's a pain to set up.