How do I get apt-get to reinstall a package and run the set up scripts?

Solution 1:

You can try with

dpkg-reconfigure -plow <PACKAGE>

This will ask again the configuration questions about the package. It may ask you to reconfigure related packages as well.

Solution 2:

Mailutils itself doesn't really have any specific configuration, as it's merely a collection of various mail utilities.

One of the dependencies of mailutils is the default-mta package which in ubuntu, is postfix. Postfix would have gotten installed when you ran apt-get install mailutils, and it's the postfix configuration screen you likely saw.

To re-run this configuration wizard, just run: $ dpkg-reconfigure postfix.

Solution 3:

You have two possibilities, reinstall the package (maybe you have to purge it and install again) or just reconfigure it (this is preferable):

dpkg-reconfigure mailutils