I receive Error 550 – Rejected or Blocked Email when sending mail

September 12, 2017     0 comments

When an email you sent bounces with Error 550 Message Rejected (or blocked), it means a spam filter has blocked the message. That is because your email domain is listed in what’s called a Real-time Blackhole List (RBL). In such cases, you will 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 domain name using MXToolbox. MXToolbox will scan your email domain against over 100 blacklists.

If your domain is blacklisted, you must contact our support team immediately and we will request a delisting from the RBL. Please 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 has 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.


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