MailPixel

MailPixel is a free hosted email-pixel workflow for important one-off correspondence. Generate a private tracking link, add the remote image to a message you send, and check the results page for image requests. Read the results as technical signals, not proof of reading: Apple Mail Privacy Protection and Gmail's image proxy can fetch images before or without a human open, caching hides repeat opens, forwarding mixes in other readers, and clients that block remote images record nothing. Test with an inbox you control, pair any signal with a real reply or confirmation, follow applicable privacy rules, and stop tracking anyone who opts out.