Thank you very much. Today, strange enough. All the php mail() went through with the original free SMTP server. I did not change anything, except once in a while Mcafee did some automatic upgrades.The only exception is in <?php$to="someone@yahoo.com";$subject=$_REQUEST["subject"];$email=$_REQUEST["email"];$message=$_REQUEST["message"];mail($to, $subject, $message, "From: $email");echo "Mail sent";?>$to and $email cannot be exactly the same email address, like both are someone@yahoo.com. If both are the same, the mail still went through without error, just I cannot receive the self-mailed mail in my yahoo account. If one is a@yahoo.com, another is b@yahoo.com or b@comcast.net, the mail would go through, and I could get all the mails in my yahoo account.