The SMTP error 511 often relates to the recipient’s email address. It indicates that the SMTP server has recognized the address as invalid. Which can occur due to a typo in the address or if the email doesn’t exist.
In some cases, the error can occur due to incorrect DNS records. Most SMTP providers require users to add DNS records for domain verification and to improve email deliverability.
If there is a mismatch between the DNS records from your SMTP provider and the one on your site’s DNS settings, you’ll likely encounter this error.
Resolving the Error – Solution
To resolve this error, we suggest reviewing the recipient’s email address to confirm if there’s a typo in the address. This includes checking the spelling of the name and the domain extension.
If the email address is correct and you’re still experiencing the error, we recommend checking your DNS settings. Ensure that the DNS records you added to your domain host match the one provided by the SMTP service you’re using.