Does Mailspring automatically reject read receipt requests on incoming mail?
Mailspring doesn’t handle MDN-style read receipt requests (the Disposition-Notification-To header) at all - it neither sends a receipt back nor sends an explicit rejection. The header is simply ignored, so the sender’s client never hears anything, which most clients display as “no receipt received.”
The “read receipts” feature in Mailspring is a different mechanism: it’s a tracking pixel in messages you send, which is why it works regardless of the recipient’s client. There’s a write-up of how that works here: Privacy and read receipts / link tracking — Mailspring Documentation