The more you stray from a standard install the less chance you will have with being successful during upgrades, getting support, etc.
I have never used iRedmail, but isnt it a postfix/dovecot/amavis/clam stack of open source products? These are all the same ones used in ispConfig but without the iredmail interface, you would use the interface builtin to ispConfig.
ispConfig has all the pieces you need to control your website inside the box. Just bring an empty server or vm.