Image inside mail body for Thunderbird email client are not detected by email prevent and OCR.

Products

• Data Loss Prevention Network Monitor and Prevent for Email

Issue/Introduction

-- Email sent with image as attachment are detectable with OCR.
-- However, if same image is added in body of email, detection/block is not working.

Environment

DLP network prevent for email and OCR.

Thunderbird email client

Cause

Thunderbird email client by default send email in inline ascii format due to which OCR never gets image to extract text.

Resolution

Advanced settings in thunderbird  that influence the detection behavior,

Workround : 

 

two advanced settings in  thunderbird  that influence the detection behavior. Suggested customer to test.
 
Change below settings. 
A. Ensure Email is Sent in HTML Format:
---- In the sending format settings, select 'Only HTML'.
B. Set mail.strictly\_mime to true (Advanced Users):
--- Go to Settings > General, scroll to the bottom, and click Config Editor.
--- Search for the preference mail.strictly\_mime.
--- Change its value to true.
C. Close thunderbird.
D. Open thunderbird.
E. Test with Image pasted in the email body.