Does anyone have any experience with Plesk 9 and JMS? I like the idea of using a domain alias for JMS but that is not an option since Plesk does not allow the creation of an email of an alias. I have read that I can edit the vhost.conf files here:

www.gadberry.com/aaron/2006/02/09/plesk_vhost/

and this will allow the use of symlinks. Has anyone use this? Thanks.

When you create separated domain, you will have separated directoriy associated to this domain.
You have to check that your server accept the Symbolic Link.
You can use the procedure "Hello World" describe in how to test configuration /faq#sec-75

If you are allowed to use Symbolic Link, you could deploy the slave site into the specific directory.
See also the JMS concept in video tutorial step 0 and in particular the summary
www.jms2win.com/tutorial

I thought of a way to avoid symlinks as I was setting up a test server. My goal was to allow normal email creation through Plesk for the slave sites. Normal operation of plesk does not allow mailbox creation on a domain name that is used as an alias.

I ended up adding a domain name and unchecking www upon initial setup. Then I setup a redirect from domain.com to www.domain.com. Next step was to add the alias to the master domain as www.domain.com. This allows setup of emails and normal use of JMS.