PopBox form submissions ending up in same gmail conversation

Thanks in advance for any help you can provide!

I use PopBox as the contact form on my website. Unfortunately, I cannot figure out how to make each contact form submission end up as an individual conversation in my gmail account.

For example, I receive messages from six different potential clients, but they all end up in the same gmail conversation, instead of separate conversations. This makes things very confusing, because we end up with single conversations that have multiple clients in them, and dozens of replies.

Is there anyway that I can modify my PopBox form, so that each submission using it ends up as a unique conversation in gmail?

Thank you!

Peter