Thank you for your input, however this can also be noted in input.mozilla.org.

As for the printing issue, what steps have you already taken, or do you have a reference thread we can take a look at?

Is this the only site? Does CTRL+P work? What did Office 365 support say?

I don't have access to Office 365 but I imagine it is somewhat like the Outlook.com consumer interface and somewhat like Outlook Web App.

Because email messages may be displayed in a page full of other content, many mail systems offer a specific printable layout, accessed either with a printer icon or on an action menu. Can you find such an icon or menu item to open a printable view? You may need to double-click the message to launch it in its own window first before the button/menu item becomes visible.

A printable view may open in a separate window, so if nothing happens, you might need to turn off Firefox's popup blocker or make an exception allowing the site to open popup windows.