I started getting reports from users within my organization about Microsoft Outlook not responding for a while after replying to an email.
After asking my staff, I found out that this issue occurred after updating Endpoint Security 11.1.2039.2.
I was not sure about this at first, but after I found this thread, I realized that many people have the same problem.
I have temporarily disabled Integrate in to Microsoft Outlook
To fix this urgently.
I hope this issue will be permanently fixed in the next update.