I would like to add a notation to an email, or be able to change its subject line without sending it again.

Here is how I would use that: I am running a technical support email inbox and voicemail. I keep email folders for individual customers so I can have all of our communications in one place.

When voicemail comes in, the recorded message is sent via email to the inbox. When it gets to the inbox, it has a subject line generated by the voicemail service. So by looking at it, I can't associate with a particular customer: I have to listen to the message. I would like to be able to edit the subject line to indicate who the caller is and what it is about OR to add some sort of meta-data to the message that I can then use in deciding which folder to store the email in.

That is my problem: I would be open to any new (or existing) facility that would aid me in organizing these email messages.

Thanks-