PHP Mail Form returning: Invalid address: (from): root@localhost"

Hi,
Thank you for the great template.
I have some problems with the email form.
The working page is https://oko.gallery/J_Art_0001.html

By using "sendmail.php" with or without SMTP lines activated I get the following eror:

{ "alert": "error", "message": "Email could not be sent due to some Unexpected Error. Please Try Again later.
Reason:
Invalid address: (From): root@localhost" }

I have configured "sendmail.php" as advised:

$toemails[] = array(
'email' => '@oko.gallery', // Your Email Address
'name' => '' // Your Name
);

as well as SMTP

$mail->IsSMTP();
$mail->Host = "mail.oko.gallery";
$mail->SMTPDebug = 0;
$mail->SMTPAuth = true;
$mail->Port = 587;
$mail->Username = "@oko.gallery";
$mail->Password = "*******";

When using "form.php" with similar alterations I get the following with and without SMTP lines:

{ "alert": "error", "message": "Bot Detected! Form could not be processed! Please Try Again!" }

Please let me know what could be the problem?