Fonts display 'fat' on external display in Outlook, but only for sent/received emails - not for drafts

I recently purchased an M3 MacBook Pro where I use Outlook as my primary email application. I noticed right away that bolded fonts in my inbox appear extra bold (thicker and almost blurry in some cases). I initially wrote this off and tried to ignore it as one of the downsides of using a MS Office product on a Mac... but I recently discovered it isn't purely an Outlook issue.

I'd been primarily using my MacBook via an external display (connected via HDMI), and recently realized that the "fat font" issue only occurs on this display. When I drag Outlook over to my Mac's display, the fonts are crystal clear. So then I figured it was a monitor issue... BUT, I also realized that when an email is in draft mode, the extra bold / fat font does not show up. For example, my signature block (and many others that come into my inbox) includes bold formatting. When I start a new email, the draft shows a very clear presentation of my signature block. However, once I hit send on that email, I can review the exact email I just sent in my "Sent" folder, and all of a sudden the text is super fat / hard to read. It seems the issue only shows up in my Sent/Inbox folders, and only while on my external display. I figured this was an issue with the font smoothing or something like that occurring in the background between my Mac and my external display, but I'm confused why the issue doesn't show up in draft emails in the very same Outlook app as it does for my inbox/sent folder?