> ## Documentation Index > Fetch the complete documentation index at: https://docs.pocketsflow.com/llms.txt > Use this file to discover all available pages before exploring further. # Resends and subject tests > Send an email again to the people who did not open it, and test two subject lines before the big send. Two ways to get more people to open your emails, on any campaign under **Marketing → Campaigns**. Both are part of the **Growth** plan and above. ## Resend to non-openers On a sent email, the **Resend to non-openers** card shows how many people received it, opened it and have not opened it yet. It starts as "In case you missed it: …" followed by the original subject. 24 hours, 48 hours (the default), 72 hours or a week after the original send. If that time has already passed, it goes out in 10 minutes. The resend goes to everyone who received the email and still has not opened it when it sends, and is still subscribed. You can cancel a resend until it starts. Once it is sent, the card shows how many people it reached and how many opened it, with a link to the resend itself. Each email can be resent once (a resend that failed can be scheduled again). ## Subject line test On an email you have not sent yet, choose **Test subject lines**: 1. Write **subject B**. Subject A is the email's own subject. 2. Pick the **test group**: 10%, 20% (the default), 30% or 50% of the audience, split in two equal halves at random. 3. Pick when to **pick the winner**: 1 to 24 hours later (4 by default). A and B go out right away. When the time is up, the subject with the higher open rate wins (a tie keeps A) and goes to everyone else in the audience automatically. The email's page shows both subjects with their opens, the winner and the send to the rest. ## How opens are counted Every campaign email carries a tiny tracking image. The first time it loads counts as one open for that person, so open rates are **unique opens**. Mail apps that block images count as not opened, and some privacy features load images for the reader, so opens are a strong signal rather than an exact count. ## Sends and limits Resends, both test groups and the winner's send are normal sends: they count toward your plan's monthly emails and go through the same checks as **Send now** (verified sender, audience size, monthly allowance). A subject test checks that the whole audience fits before anything goes out. Developers: see [Resends and subject tests API](/api-reference/resend-and-subject-tests). This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.