causing problem to outlook

Hi.

A client system running SEP 12.1 has problem communicating with Mail Server.

client machine stops pinging the mail server at any time.

for the solution, we restart PC, the problem is gone.

after some time it again stops pinging mail server.

After outlook and PC troubleshooting, I had to remove SEP from clinet machine and installed other free antivirus.

outlook is working fine all the time since then.

I am still skeptical on what is causing in SEP to occur tihs issue.

Please guide.