Question marks in boxes in mail

After two hours on the phone with Apple support we narrowed it down to a font issue. I am a commercial printer and use Suitcase Fusion to manage my fonts. I went to their website and found if there are two Arial fonts turned on at the same time there could be an issue. The arial font was turned on in my system fonts but was another arial font was also turned on. When I turned it off, all the little boxes and arrows went away and was replace by the information that was supposed to be displayed in the email. Hope this helps someone out there!

I am connected to the internet and it is in many emails not just a few so there must be something going on. Seems like it had happened since I downloaded the new Firefox update. I tried using that as my browser preference but didn't like it so went back to Safari. Has happened many time since that. Thanks to anyone for assistance.

Already tried that. It is checked. Thanks!!!