Hi this.to.firstName,

referral.name recommended I contact you. My name is this.fullName, and I'm currently working at company.name. referral.name thought very highly of you and encouraged me to reach out.

I understand that you are currently working on project.name. At company.name we are doing some interesting work in this area, and as such, believe there's an opportunity for us to collaborate together.

Do you have time for a short call? If so, would any of these times work?
If those don't work, no problem -- just let me know what days/times would work for you.

Looking forward to hearing from you soon.

Regards,
this.firstName