A kind reader pointed out to me that my Atom feed was incorrect. There were two problems. First, I was specifying an incorrect URL in the feed’s <link rel="self"> – it was pointing to a nonexistant feed.xml file. Second, I was omitting a <link> tag from the entries entirely.

Thunderbird didn’t like this. With no <link> for an entry, it would show the feed’s <link> in it’s UI. And that link left users at a 404 page.

I pushed a fix this morning. You might have to refresh or resubscribe to pick up the changes.