Hi,
DLP Outlook plug-in is disabled on these machines so try following option to make them enabled.
1) Go to Enforce->Agent Configuration page
2) Disabled outlook monitoring.
3) Make sure that outlook monitoring is disabled.
4) Enabled outlook monitoring.
5) Restart Outlook application on the machine.
To find out root cause we need system information to check is there any compatibility issues with other thridparty outlook add-ins.
What version of DLP agent you are using?
Not all the agents have this issue so could you please tell me what other softwares are installed on these machines showing warning message and what version of outlook they are using?
Thanks
Dhananjay