I find it a bit annoying that I have to re-enter my password twice every time I (re-)start mutt when I want to update my configuration file. Well, it appears I don't need to be doing restarting mutt. The MuttWiki describes a way to re-load the configuration after mutt is running. Type the following into mutt after you've changed your muttrc file:
Note that shell expansions may not work---you should spell out the full path.