If you need to enable wildcard domain on your Parallels Plesk Panel 11, here is how to do it.
Step 1
Login to your Parallels Plesk Panel 11 and go to Hosting Services -> Subscriptions -> Yourdomain.com -> Websites & Domains. Click on “Add New Subdomain“.
In the field “Subdomain name” you enter * and in “Document root” field it should say httpdocs.
Click OK. Wildcard domain should now be working. If not, follow Step 2.
Step 2
If Step 1 did not do the trick. You need to login to your server as root user and run the following commands:
/usr/local/psa/admin/bin/httpdmng --reconfigure-domain yourdomain.com
service named reload
service httpd reload
You could use a tool like PuTTY to login to your server and run commands.
Known issues
If you are running WordPress multisite with the domain mapping plugin and your custom domain(s) keeps redirecting back to your main domain. Here is how to solve it:
Login to your Parallels Plesk Panel 11 and go to Hosting Services -> Subscriptions -> Yourdomain.com -> Websites & Domains. (I’m assuming you’re already added your domain alias). Find your domain alias and click on “Hosting Settings“. Uncheck the “Redirect with the HTTP 301 code” option and click OK.