Thanks, but I tried that. I selected Thunderbird as my default mail application (from within Mail - the only way to do it I believe). Opened up iPhoto and selected the mail option. It fired up Mail anyway. Also, Thunderbird still did not show up as a choice on the mail options drop-down.
So I put Mail in the trash to take that option away from iPhoto. I then selected the mail option in iPhoto and it asked me to select the application to use. I selected Thunderbird but iPhoto would not launch it. I received the following error message:
"thunderbird-bin got an error: Can't make a <<class bcke>>.
So I went back to iPhoto and tried again. When asked to select an application to mail with I selected GyazMail. This time iPhoto actually launched Gyazmail but thta's all it did. It did not initiate starting a new e-mail. Instead I received the following error message:
NSCannotCreateScriptCommandError
So it seems iPhoto (Apple actually) insists on only the limited options I listed previously (Mail, America Online, Eudora, and Entourage). Not very flexible, in my opinion. And a bit Microsoft-esque.