If your email server has been blacklisted, there are several steps you can take to resolve the issue. Here’s a list of some of the things you can do:

1. Check that emails from your server are being sent on time.
2. Search online related blacklists to verify if your server is indeed blacklisted.
3. Check whether your email delivery rate is lower than expected.
4. Increase filtering to reduce the amount of emails that bounce.
5. Review your server’s IP address with your ISP (Internet Service Provider).
6. Fix or disable any insecure login scripts for your server.
7. Debug scripts that send emails from your server.
8. Change your email address and/or server name.
9. Monitor your email server’s error logs regularly.