How to fix Error 550 Message Rejected on your email

When you receive an Error 550 Message Rejected (or blocked) when trying to send an email, this means that a spam filter has blocked the message. This error is occurring because your email domain is appearing in a Real-time Blackhole List (RBL). In this case, you’ll have to take action to have your email whitelisted as non-spam.

Is my email domain blacklisted?

To determine if 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 that they remove you from the list. Please be aware that delisting takes time.

How do I prevent my domain email from being blacklisted?

Email domains can be blacklisted due to malware 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.

Your email domain can also be blacklisted when your company’s web application is exploited through malware or a virus and used to send spam emails. When this happens, your web app sends out spam using your domain name, causing the domain name to get blacklisted.

Keeping hackers out of your web application

Here are some tips to prevent hackers from hijacking your web app:

  • Keep website software updated, and 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 ten 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.

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