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Fixing the 550 5.7.1 [RST] error

If you're receiving this error, it means that the mailing list is really bad or it is possible that the account is compromised.

What can I do to resolve this?

Here are some steps you can take to clean up the email coming from your account:

    1. Secure your account against compromise by spammers:
      • Change your password. Ensure your new password has a minimum length of eight characters and uses a mixture of upper and lower case letters, numbers, and special characters.
      • Verify that your operating system is running with the latest security updates.
      • Update your anti-virus software and conduct a full scan of your system to ensure that a spammer has not installed spam-sending malware on your computer.
    2. If you have recently sent a newsletter or other type of mass mailing from your account, verify that none of the URLs within your messages have been flagged by anti-spam systems. Use the Trusted Source URL check to check a URL or domain's reputation. Generally speaking, make sure you are following best practices when sending a bulk campaign, such as using an opt-in only mailing list.
    3. Sanitize your mailing list and ensure you are sending mails to only receivers who have opted in to receive your mail.

If this is a false positive, please raise a support ticket by writing to with the following details

1) Sender email address

2) Subject

3) Recipient email address

4) Date & Time 

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