Since I feel called out by Rachel's recent blog-posts.

rss2email works in two ways:

• Fire and forget: invoked by cron at the users's schedule.
  • It will process all the feeds once, then terminate.
• Deamon: run constantly sleeping between fetches.
  • This is the ideal place to add the support.

We have the boltdb for storing state of entries, I guess we can use that for storing etags, or we can just store in RAM - one string per endpoint - that might be quicker I guess in-practice that's fine. We'd make one "raw" request on first-poll, and after that we'd save memory. That perhaps is the pragmatic way to go.