yes its safe to work, if you have any software on your system that uses port 25, you need to unlock this -- we found this out the hard way with GFi Faxmaker, it needs to use SMTP port to send our faxes to the Exchange Fax mailbox as PDF's, and that port got blocked by McAfee's default install.
Used PRP to set the policy to do this, you could do the same, so only certain machines that need this get it unlocked via ePO (I'm guessing here). PRP only offered basic policies, so it was all or nothing, one Workstation and one Server policy options.