Differentiating incoming emails from same form

I have a client who's getting 40-50 emails a day via his site's FormM@ailer. He's looking for ways to help the person dealing with them all to more easily sort and distinguish them. Right now they all have the same subject line and when they get forwarded GoogleMail thinks they're all one thread and embeds the "thread" in each forward quickly becoming unmanageable.

He asked me to come up with a solution. His suggestion was to try one of these ideas but I don't know if they're possible with FM...
1) Have a code that will date/time stamp the subject line when sent
2) Have the subject line blank but be a required field for the sender so it's always unique.

Any way to do either of those? Any better ideas?

I know there's a way to have a drop down list of recipients to choose from. I haven't ever done that. But I'm guessing that would set each one up with a different config number...then each of those could have a unique subject line. So that might be a solution. The problem is that the sender would have to accurately direct their email rather than the one person receiving them all and deciding who to forward to.

Thoughts?
Thanks!
Sheila