You may run into this error if the recipient's SMTP server cannot interpret parameters associated with the "MAIL FROM" or "RCPT TO" commands.
Since this error occurs on the recipient's side, there is nothing you can do about this. However, you can wait a few hours and resend the email to see if the issue has been resolved. If the error persists, you may have to contact the recipient server's administrator for troubleshooting assistance.
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