Hi, Matt S Rinc here, I can help you with creating your template. I have experience with creating templates manually and using custom software and (will) definitely know how to create it for you.
Please provide me best, last version of your mock-up and company branding if you have. Though I am not a graphic designer I do manipulate images as much it's possible with software and work with HTML from 1994.
I am writing this on a MacBook Pro using latest version of Apple Mail (and OS X) so will test a template thoroughly.
Looking forward to your reply,
Matt