ContentThe message “invalid HELO command” means that the application you are using for sending mails does not comply with corresponding RFC standards. This happens rarely and the only solution is to use another application for sending mails. Was this article helpful to you? Related Articles Error: Too many recipients Cannot send attachments The recipient did not receive my email and I did not receive it bounced back 503 Valid RCPT command must precede DATA What is the limit on the maximum size a single email may have? Do I need a valid email account to use sendmail? Hasan Ali Posts Website Leave a Reply Click here to cancel reply. Name (required) Email (will not be published) (required) Website Comment