When an email you’ve sent bounces with Error 550 Message Rejected (or blocked), a spam filter has blocked the message. That’s because your email domain appears in what’s called a Real-time Blackhole List (RBL). In such cases, you’ll have to take action to have your email whitelisted as non-spam.
Is my email domain blacklisted?
To see whether your email address is blacklisted, check your email domain (the part of your email address after the @ symbol) using MXToolbox. MXToolbox will check your email domain against over 100 blacklists.
If your domain is blacklisted, you must contact the blacklist itself and request delisting. Be aware that delisting takes time, so be patient.
How do I prevent my domain email from being blacklisted?
Email domains are often blacklisted due to malware that’s been installed on your computer without your knowledge. Run a malware check and removal app such as Malwarebytes to verify your computer is clean and healthy. Keep your anti-virus software up to date, make sure your computer has the latest security updates, and change your email password just in case.
You can also get blacklisted when your company’s web application is exploited through malware or a virus and used to send spam email. When that happens, your web app sends out spam using your domain name and the domain name itself gets blacklisted.
Keeping hackers out of your web application
Here’s what you can do to prevent hackers from hijacking your web app:
- Keep website software updated. Make checking website software a daily routine.
- Prevent SQL injection attacks by parameterizing SQL queries.
- Validate forms data on both the client and the server side.
- Use strong passwords of at least 10 characters and make sure your web application stores those passwords as encrypted values.
What do I do if I’m still blacklisted?
If the steps above fail to delist your email domain, contact HostPapa Support for immediate assistance. In your support ticket, please include your email address, the email address you were mailing, the subject line of the rejected email, and the date and time it bounced.