The 550 5.1.1 error

There are several possible reasons that you received this error. In this guide, we'll talk about the reasons and help you resolve this nasty error.

Reasons for the 550 5 1 1 error

  • Invalid email address. You may have an invalid recipient’s address, meaning that the address was active when you got it, but now it no longer exists, that’s why your email can’t be delivered.
  • Typos in the email address. Any mistake, even a missing character can lead your email failing to send, since the address doesn't exist.
  • Misconfiguration. Any bug or misconfiguration of the recipient’s server may prevent them from getting your email.
  • Outdated DNS record. DNS settings may be incorrect for the recipient’s domain, that’s why MX can’t resolve correctly.

How to fix the 550 5 1 1 error

  • Make sure there are no spelling mistakes in the recipient’s email address and check if it is still valid. There are a lot of tools available for this purpose. Make use of them!
  • Your DNS record is outdated, and the recipient’s server can’t resolve it. Update it! You can use DNS Lookup to get to know if there are any problems.
  • Still, having checked the email address validity, you see that everything is alright, but you continue receiving the 550 5.1.1 error message. In this case, contact the email address owner and inform on possible problems with the mail server configuration settings, stating that you have done everything from your side.

Avoiding the 550 5 1 1 error message when sending bulk email campaigns

If you regularly send bulk email campaigns to a large number of recipients, you may receive this error relatively frequently. If you send emails to invalid email addresses, it means that you don’t know who you are sending to. Thus, email providers consider your emails to be spam, and, as a result, you receive the 550 5.1.1 error message. Moreover, today, it is easy to gather many email addresses, using specialized software like “harvesters” or “harvesting bots.” So, providers are partially right. But, to avoid this problem, make a habit of regularly checking the email addresses, you have to keep your mailing lists clean.

The most common 550 5 5 1 messages

  • 550 5.1.1: The email account that you tried to reach does not exist
  • 550 5.1.1: Recipient rejected
  • 550 5.1.1: User unknown
  • 550 5.1.1: Recipient address rejected: User unknown in virtual alias table
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