When sharing photos via email in PBU you will encounter various options pertaining to the quality of the original photo as well as the quality of the shared photo.
In the Event Manager
Set your Email Sharing Option to 'Attachment'. This will ensure that your photos render correctly on the largest variety of devices with minimal compression
In the Options tab, set your Image Sharing Size to Large or Original
When configuring your Camera Settings, you will want to choose Middle Fine or higher
NOTE: If the digital files on your hard drive are clean, but the photos being delivered via sharing are not clear, then your Sharing Options need to be adjusted as compression is taking place. This may also be the individual device the photo(s) are being sent to or carrier settings.