I need to be able to report on emails in Salesforce, furthermore I need to be able to see the size of the email, is there a way to do this? I cannot find a report type that allows me to report just on emails. If I look at the report type emails with cases, I cannot find a field associated to the email object that indicates its size.
If you create a new Custom Report Type based on Cases with Emails as associated object, it does let you pick the 'Message Size' field on Email.
Other emails are not stored in the same place as Case emails, indeed. They are usually events with attachments. There is no standard reporting available on attachment (size), so you'd need apex/visualforce.
Hira Lee created a free packaged solution for it: https://success.salesforce.com/answers?id=90630000000gsMYAAY (bottom of the page)