Most websites have more than a single domain or host name pointing them. Even if you only have one domain, your site is most likely available at domain.com and www.domain.com. For Search Engine Optimization (SEO) you should set a preferred Canonical Domain. This will force all traffic to use your preferred domain. So, if someone has a link to your site using domain.com and you have set www.domain.com as your preferred domain, the link will still work but when the user gets to your website, mojoPortal will adjust the url to use www.domain.com.
To enable forcing a preferred host name in mojoPortal content management system, you need to set this as true in your Web.config or user.config file:
<add key="AllowForcingPreferredHostName" value="true" />
This will make the setting available in Site Settings > Advanced > Preferred Domain:
In a multi-site installation, this can only be set from the root admin site, but you can set it there for any site. Be very careful with this setting, the reason its disabled by default is because it will force a redirect to the entered host name and if you put in an incorrect host name you may not be able to access your site without fixing it in the database.
If you are in a situation where you need to alter this setting via the database, the value is stored in mp_sites.apikeyextra5.
So, for example, you could clear it out by using
SET ApiKeyExtra5 = ''
WHERE SiteID = [yoursiteid]
You could leave out the WHERE clause if you want to remove it from all sites, or if it is a single site installation.