The reason you add email to the safe senders list is so that it doesn’t get marked as junk
In an Exchange 2010 Environment, the exchange server applies individual addresses (not domains) added from Outlook to the server safe senders list.
Right click any message in Outlook and go to Junk E-mail Options
Select the Safe Senders tab
At the bottom, there are two options that automate a lot of the process:
a. Put a check-mark box in Also trust e-mail from my Contacts
b. Put a check-mark box in Automatically add people I e-mail to the Safe Senders List
If there is an address that isn’t in your contacts that you want to add Click the Add button. Enter the full email address. Domains are not accepted by the exchange server. then click OK.
Select OK or apply to save all changes.