I like to know how to reduce the size of a photo in iPhoto which I will attach in an e-mail.
click on the photo you want to send
click on the icon Mail (bottom right)
a window called "Email photo (s) by mail" opens
choose the size ( small, medium, or large size) and look at the information just below "approximate size". You'll know the new size of your picture
click to write to a text with the photo
To know: the size of emails is limited. To be sure of not seeing his email rejected as too large, it is best not to exceed 3 to 4 MB
For what is the problem with Mail and your correspondents who cannot read attachments, verifies this Mail to:
open the Edit menu / Attachments
tick if necessary "Always insert attachments at end of message"
check if necessary "Always send attachments compatible with Windows"
And then you can ask your friends make a right click on the photo sent and use the menu to save the photo. Come on, let's be mad to try their request outright drag and drop: they select the photo and maintaining the click down, they slide the photo on the Windows desktop and then finally release the mouse click. Normally, the image is copied onto the desktop (on Mac it works very well in any case!)