I have partner accounts and partner users. When we assign opportunities to partner users, we simply change ownership. However, we often need to assign opportunities to contacts who are not on Salesforce as partner users. They do exist as contacts under the partner account though.
On my opportunity layout, I have a lookup contact field (where we select the NON-Partner user). This tells us who we assigned the opportunity to, and which partner account.
What I would like to do is send an email with opportunity details to that person.