Notify client users via email of project progress

Notify client users via email of project progress

Hello,

I wanted to be able to send automatic EMAIL ntoifications to clients about the progress of their work based on when a task or milestone is completed for a client's project. How do I do this.  I noticed Bug has the ability to email, but i don't think i want to send out bug notices.  And No, I don't want to have to update the feeds for hundreds of clients either.