I have tried to send a blank email message to myself via BT webmail and this message popped up:
"Sorry your email could not be delivered due to content policy reasons. Please check your message content for URLs, content and subject matter that could be construed as Malware, Spam or Phishing before retrying. (6-1-1-1) ID (6A08C1FD01B1705C)"
There was no content in the message. It was blank. Only the subject line had text "Test from web email"
I've notice over the last few days when using a client (Outlook 2016 in my case) message show as sent on the application but not on webmail. This has caused me some grief, in thinking folk had received emails but they ahd disappeared.
Help and advice welcome. BT email regularly lets me down!!