Ask HN : How to turn quote requests into paying clients?

It's been a while since I am getting unexpected quote requests. The subject line states "quote". While most of them are with little info about actual work to be done. I have been quick replying those emails asking few questions about the work to be done, but couldn't get response. How do you handle such requests? How could we turn an unexpected quote request into a paying client?

Here is a recent one:

Hey there, We are looking for dev team that could provide programming and updates for some web apps we are planing to launch. If you are interested in long term business relationship let us know.