Most software in ports comes with some kind of configuration, usually containing sensible defaults. Nothing more general can be said about it, because the ports tree contains close to 20,000 ports contributed by thousands and thousands of people.
I advise you to always install software using the ports tree whenever it's available. This will guarantee a logical installation (under /usr/local), logical deinstallation (all installed files will be recorded on installation), dependency resolution (every dependency must be in the ports tree) and a clear upgrade path (using the right tools, like portmaster or portupgrade, you will be told when a newer version is available). So use Qmail et al. from ports.