I have multiple domains pointing to one hosting location. I wish to establish one of the domains as my main domain and therefore I wish to perform a 301 redirect to this mai
This is not really that umbraco related but I think what you want to do is this:
<rewrite>
<rules>
<rule name="redirect" enabled="true">
<match url="(.*)" />
<conditions>
<add input="{HTTP_HOST}" negate="true" pattern="^www\.example\.com$" />
</conditions>
<action type="Redirect" url="http://www.example.com/{R:1}" appendQueryString="true" redirectType="Permanent" />
</rule>
</rules>
</rewrite>
Match all urls unless the host name part is exactly www.example.com - and redirect those to www.example.com/whatever.