iPhoto 11 no longer uses an application for sending emails. It creates the emails and sends them itself when you supply your account details.
So, no, you can't set Outlook (or anything else) as a default Email client in 11.
FYI: iPhoto 11 works with email in a new way. Rather than using an Application to send the email as before, what they have done is handle the email within iPhoto. So, you input your Email Account details - the name of your service, the account name, password, etc, and iPhoto uses that information to send the email via your account.
There's an element of swings and roundabouts in this.
Users of Apps like Thunderbird or Postbox could not email from within iPhoto in the past as those apps are not scriptable. Neither could it be used by people who use Web Mail and access their mail via a web browser. By going this way these people users have the same service as Mail/Entourage/Eudora users have.
So much for the swings: on the roundabouts, however, users of Mail (and I suspect Entourage and Eudora) have a change. Share -> Email does not work as before and you can no longer select pics within iPhoto, resize them and pass them over to their preferred application. Neither can you send photos without a Template.
However, by creating a Service sing Automator, it's perfectly possible to recreate the previous usage, though accessed a little differently. Here's one way:
1. Launch Automator
2. From the Dropdown sheet select to make a Service
3. On the Right hand side, over the large pane (under the record button) select 'Service Receives +no input+'
3. From the Library Column (extreme left) click on Photos.
4. From the Middle Column drag 'Get Selected iPhoto Items to the large pane.
5. In the drop down on 'Get Selected Photo Items, select 'Photos'
6. Back to the Library column, extreme left and this time click on Mail
7. Drag 'New Mail Message' to the right hand pane, under the existing 'Get iPhoto Items'
8. Drag 'Add Attachments to Front Message' under that.
9. Save it, Name it.
Now, in iPhoto select the photos you want to email
then
iPhoto Menu -> Services -> And select the Service you created.
The Mail app comes forward with your Message, with files attached.
You can resize the Photos using the option at lower right of the Mail window:
Using the Keyboard Shortcuts in System Preferences you can choose a key command to do the whole thing from the keyboard.
I have looked at the Automator commands provided for Outlook and it seems like you could do a similar job for it - though I don't know if it will have the ability to resize the images.
Regards
TD