Why Email Attachments are Sent as HTML File Links
This is due to the way salesforce sends attachments. To conserve bandwidth (and avoid compatibility issues with some mail services), attachments over 3MB are sent as links.
e2a (or any other third party app) cannot override this behavior of Salesforce and you can verify this by creating a contact record with your email address on it, and sending yourself a 5MB attachment as an example. For more details on this please see the following Knowledge Article from Salesforce:
Why are email attachments sent as .HTML file links?
Please contact email@example.com for any questions.