I installed Mailman from a package or I followed a HowTo document. Where do I go for help?
When you install Mailman from a third party package, your primary support resource should be the packager. The packager knows what's in the package and how it should be configured. People on the mailman-users lists don't always know these things.
The same considerations apply if you followed a third party HowTo document. Plus, there may actually be errors or unaccounted for situations in the HowTo and the author should be made aware of these things. Thus, you should at least try to contact the author of the document first.