In Classic and Journal it's already selected. At least in my library. If it's not on yours change themes, check the box and change back.
If that doesn't work make a temporary, backup copy (if you don't already have a backup copy) of the library and try the following:
1 - delete the iPhoto preference file, com.apple.iPhoto.plist, that resides in your
User/Home/Library/ Preferences folder.
2 - delete iPhoto's cache file, Cache.db, that is located in your
User/Home/Library/Caches/com.apple.iPhoto folder (Snow Leopard and Earlier).
or with Mt. Lion from the User/Library/Containers/com.apple.iPhoto/
3 - launch iPhoto and try again.
NOTE: If you're moved your library from its default location in your Home/Pictures folder you will have to point iPhoto to its new location when you next open iPhoto by holding down the Option key when launching iPhoto. You'll also have to reset the iPhoto's various preferences.
NOTE 2: In Lion and Mountain Lion the Library folder is now invisible. To make it permanently visible enter the following in the Terminal application window: chflags nohidden ~/Library and hit the Enter button - 10.7: Un-hide the User Library folder.
As soon as I select any other theme it becomes selectable. When I go to either Classic or Journal it is ticked but greyed out and non selectable. I tried deselecting and reselecting it in another theme but as soon as I go back to Classic or Journal it's ticked and greyed out.
Your suggestion to delete the preference and cache files are at the limit of my knowledge!
As regards backup I run Time machine and whilst I can see your steps to delete the library and cache, I don't know how to get to User/Home/Library...
For those two themes the defraut setting is that it's selected and image files are automatically added to emails as attachments. In the other themes you have the option to not attach the image files to the email.
As for finding the library:
NOTE: In Lion and Mountain Lion the Home/Library folder is now invisible. To make it permanently visible enter the following in the Terminal application window: chflags nohidden ~/Library and hit the Enter button - 10.7: Un-hide the User Library folder.
Ok, I went to my Apple store where they deleted the preference and cache, re-installed and updated iphoto and still the same. I am booked in to rebuild the library as a final attempt to solve this.
HOWEVER from the last post it would seem that my system is working as it's supposed to, in that these two themes are permanently selected (ticked and greyed out to indicate I can't not attach)
I will therefore try sending attachments (again) to different recipients to see if the problem is only with the original recipient.
Let's make sure we're on the same page. That these did you use originally? If it wasn't the journal or classic theme was the checkbox selected?
Is this is what you're seeing for the classic and journal themes? That means attachments WILL BE ADDED even though it's greyed out.
Try creating an email with one photo, select Actual Size and then check the lower left to see what the file size of the attached photo will be.
Try sending a couple of photos to youself and see what happens.
Thanks to your help, I think I'm there!
As soon as I got your message (sent 1032) I suddenly understood how attach works differently in Classic and Journal to the other themes.
Yes the attach photos option is greyed out in Classic and Journal themes and I think I now also understand how the attachment tool works with the other themes. I hadn't known that it still sends an image but not a separate atttachment as well.
I have tried sending pictures to myself (alternative e-mail address) from Classic, Journal, plus one of the other themes (with attach both ticked and not) to both an Apple and a Windows pc. They all came through as expected.
I just want to repeat this test by sending them to someone else not associated with my system and then will be happy that actually I don't have a problem.
This will be followed by questioning the original recipient (abroad) who said they didn't get the pictures.
Whilst I have had an hour one-to-one at my local Apple store on iphoto, I didn't fully appreciate how this feature actually works - and it would appear, neither did they as I spent an hour at the genius bar where they also thought I had a problem.
Where can I find a reasonably detailed reference to iphoto so that I can understand the nuances of different features? I can only find online help and instructions that don't go into any depth.
There really isn't a treatise on all of the features and subtilites of iPhoto. There is a 3rd party manual that might help, iPhoto '11: The Missing Manual (Missing Manuals) (English and ...). You might try your local library to see if they have it and peruse it before buying. Or at a local book store.