Check this Help (F1 / Help → Index) and the Frequently Asked Questions first—many questions are answered there.
Email technical support at support@finebytes.com. You can also open that address from Help → About.
When you write, include your Magic File Renamer version (shown in the window title and in About), your Windows version, and a short description of what you expected versus what happened. For rename problems, note whether Preview showed an error before GO.
Send comments, bug reports, and feature ideas to support@finebytes.com, or use the product site contact options listed on www.finebytes.com/mfr.
See also: Website & Updates, About finebytes.