How to prevent unwanted image resizing and metadata loss.

In Apple Mail you can downsize images that you attach to a message. Unfortunately, if you do so, then the next time you attach an image to an email message, Apple Mail automatically applies the last size used. This way you often end up sending downsized images when you do not want to. Additionally, when resizing, Mail modifies the images in the following way:

removes EXIF metadata (image orientation/rotation, camera information, etc.),
changes color profile to sRGB IEC61966-2.1,
removes layers in FireWorks “PNG” files and any other proprietary data,
changes filename extensions to their longer form (.jpeg, .tiff instead of .jpg, .tif).

To prevent automatic image resizing and its above described effects, set the default size for resizing (the Downsize images to option) to Actual size (do not resize) in Attachment Tamer's Composing and Sending preferences. Mail will no longer automatically resize newly attached images.