Welcome to Apple Support Communities. We're all users here.
Let me hazard a wild guess that you're using Outlook, formerly Hotmail, for email in your web browser.
When the forced 'downgrade' from Hotmail to Outlook occurred, they decided to hide some frequently used commands and made simple message printing from a browser print command nearly impossible, at least for Mac users.
The trick is to use the Print command now hidden within the Outlook menu bar.
It's in the "..." section of the Outlook top menu bar following Categories along with "Mark Read, Mark Unread, Flag, Unflag, and View Message Source".
Select Print from there, it will open a new Outlook Print Message window. You should once again be able to print emails in their entirety.