Posted this before I got your other reply. Glad you got it working.
Outlook is not compatible with Photos. You'll need to use Mail.
Did you have Outlook set as the email client for iPhoto? If so and you're still able to use iPhoto open it and set Mail as the email client, reboot and try Photos again.
If so and you can't use iPhoto then move the com.apple.iPhoto.plist preference file that's in your Home/Library/Preferences folder to the Desktop, reboot, launch Photos and try again.
If that fails the open the iPhoto preference file with a text editor (the free TextWrangler is an excellent choice for this type of editing) and search for Outlook. then change
<key>EmailApp</key> |
<string>Outlook</string> |
to
<key>EmailApp</key> |
<string>Mail</string> |
Replace the iPhoto preference file in your Home/Library/Preference folder, reboot and try Photos again.