@ec
As someone from IT - I can attest that email size is limited except for authorized destinations. Certain attachment types can no longer be sent. Also, any kid of recognized data, such as account numbers, social security numbers will be flagged and blocked.
A simple email to test, such as the word "Testing" in the header and body should go through. Unless you are in a LOB that denies everything as policy. In IT, we didn't have that policy - we used emails to communicate with vendors all the time. (Cisco, Arista, Microsoft, etc)
Because we use a proxy system, your email will be intercepted, decoded, and sent on if it passes the filters. If you are blocked, you and your boss will likely get a notification.
Also, certain names, such as leaders of the firm are a reason to block emails if mentioned anywhere in the text. If you send something with chainsaw's name in it, you, your boss, and even higher get notified. And likely put on a risk list which will further squeeze whatever email privileges you had.
Something to think about.