I love that Buttondown lets you set a canonical URL for each newsletter you send out, that way you can have a blog post at your website with the same (or similar) content that gets the traffic when subscribers click for a web version.

screenshot showing Buttondown’s settings for an email newsletter with the option to set a canonical URL: If you're publishing a newsletter that mirrors another publication or blog that you own, you can add a 'canonical URL' here. This will help search engines understand that your newsletter is a mirror of your other publication, and drive traffic from the emails to your other publication.