phpmailer - The following SMTP Error: Data not accepted

Interestingly, I had the same exact issue and for me the problem was that my connection was timing out. To be able to see more details on my connections, I added $mail->SMTPDebug = 4; to my phpmailer (look up how to capture the debug since the default output function is echo).

Here's the result:

SMTP -> get_lines(): $data was ""
SMTP -> get_lines(): $str is ""
SMTP -> get_lines(): $data is ""
SMTP -> get_lines(): timed-out (10 seconds)
SMTP -> FROM SERVER:
SMTP -> ERROR: DATA not accepted from server: 

The default timeout is set to 10 seconds. If your app can support more, add this line to your phpmailer:

$mail->Timeout = 20;

set phpmailer to work in debug to see the "real" error behind the generic message 'SMTP Error: data not accepted' in our case the text in the message was triggering the smtp server spam filter.

  $email->SMTPDebug = true;

For AWS users who work with Amazon SES in conjunction with PHPMailer, this error also appears when your "from" mail sender isn't a verified sender.

To add a verified sender:

1. Log in to your Amazon AWS console: https://console.aws.amazon.com

2. Select "Amazon SES" from your list of available AWS applications

3. Select, under "Verified Senders", the "Email Addresses" --> "Verify a new email address"

4. Navigate to that new sender's email, click the confirmation e-mail's link.

And you're all set.

your server dosen't allow different sender and username you should config: $mail->From like $mail->Username