Blocking Outlook External POP/SMTP

["Hart, Lee Anne" <LeeAnne.Hart () montgomerycollege edu>]

Hello,

I'm looking for information on preventing/prohibiting users from utilizing
Outlook (at work) to retrieve their personal email from Gmail, AOL, Yahoo,
Comcast, Verizon, etc.

Looking for the following:

* Reasons why users should not be allowed to use Outlook on their work
computers to retrieve their personal email.

* Tools/techniques to block this type of traffic. It seems the most common
ports are 110, 465, 587, 993, and 995. Are there others? 

Any reference are much appreciated. 

Thank you!
Lee Anne

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