Hey {{contact.first-name}},
I've been following [website name] for a while now and have always admired your commitment to providing valuable insights to your readers.
I recently published an article on [topic] that I think could complement your existing content nicely. I'd love to offer it as a guest post for your blog.
Would you be interested in featuring it? I believe it could provide additional value to your audience while also helping to boost both our sites' SEO.
Let me know your thoughts!
Best,
[your name]