Hey {{contact.first-name}},
I stumbled upon your website and really enjoyed your content on [topic]. It's clear you put a lot of effort into creating valuable resources for your audience.
I noticed that you mentioned [topic] in one of your recent posts. I've actually written a comprehensive guide on that same topic and thought it could be a great addition to your content. Would you be interested in taking a look? If you find it valuable, perhaps we could discuss the possibility of featuring it as a guest post on your blog.
Let me know if you're open to the idea, and I'll be happy to share the guide with you!
Best regards,
[your name]