This letter follows up the first strategic alliance letter, assuming you've received no response to the first. It should address some of the more obvious concerns a potential alliance partner may have.
1234, Main Street
Boston, MA 02123
<Recipient Address Goes Here>
On <first letter date>, I sent you a letter proposing a strategic alliance between Abc Company and <other company name>. To date, I have not received a reply from you regarding this important matter. In case the first letter was mislaid or you've simply been too busy to respond, I thought I would contact you again.
Of course, you may simply have reservations about teaming with a company that you may have seen as a competitor. Please be assured that I and Abc Company want nothing more than for both our companies to thrive and profit. We feel that by <proposed action>, both our companies will benefit.
I trust you can see the obvious benefits of this sort of arrangement. Please take the time to call me at <phone number> and set up a meeting. I'll explain our ideas and show you how everyone will be thrilled with an alliance between Abc Company and <other company name>. I hope to hear from you soon.
encl: <List of enclosed items goes here>