DLP Mac Symantec web add-in for outlook preventing email from being sent

Products

• Data Loss Prevention

Issue/Introduction

Randomly, when trying to send an email via Outlook, the following message appears in the Outlook application:
"The Add-in Symantec for Outlook is preventing this message from being sent"

After waiting a few seconds, hitting 'send' again shows the email is sent successfully.

DLP logs do not show any detection occurring at the time the message was triggered. Logs also do not show any errors.

Environment

Symantec Data Loss Prevention 16.1.x, using Microsoft to deploy the DLP add-in to Outlook
Exchange Online, New Outlook version 16.101.1
MacOS - Sequoia (15.x)

Cause

Third party application on the workstation was causing loopback traffic, resulting in Outlook generating the message.

Resolution

Work with Third Party Application vendors to exclude application traffic that may cause loopback.