Mine just updated too. Couldn't read a thing. This fixed it:'

Top menu - View - Font Size - Increase Font Size

(and maybe also View- Density - Relaxed)

This new layout is absolutely awful. I increased the font size (thanks to the tip on this thread), but it still hurts my eyes to look at it. It's like, with the new font style / appearance, there is such a sharp contrast between the bold and non-bold words in my inbox that it hurts my eyes. I don't know why they had to go and mess with something that wasn't even broken. This new update is awful.

I agree. No matter what the font size is (and I expanded it quite a bit), the list of emails is unreadable because each line is too close together and the font is jarring. This alone could cause me to switch to another email interface.

Wait - try changing the font density from compact to default or relaxed: View > Density > Default or View > Density > Relaxed. Either of those will be easier on the eyes.

i agree aswell, font choice ishorrible and the size aswell. all is very contrasty. nothing compare to older version. why always change something that is good ?.... this is anoying all toolbar is different, all layout aswell. button download message is gone from top left... come on guyz and you want donation ?..... now i have to change density like if i was 95 years old, font is awfull... by default.

How the h--- do I change the actual font for both the incoming mail subject / date / correspondents list AND the side panel with my email inboxes, folders and subfolders?

I had a nice easy to read DejaVu Serif and since the recent glorious update it's back to Arial or whatever that sans-serif font is. Serif fonts like DejaVu and Courier are easier for me to read. I am worried that this may have been something that could only be changed through a now-obsolete add-on.

Bluejay

'Have the same issue. Any emails coming in with imbedded materials is so tiny, it's unreadable. Attempts to change those fonts either with the 'view' or shift/control/+ doesn't work. It's a crap shoot when replying to emails what the font size will be, or which will be received. I had a friend exchange emails with me, and what i sent was enlarged, and what he received was microscopic. This is maddening!

I had started to draft my own issue to post to the forum, but see that it is exactly what bflodave described above, so I will put it here and hope someone has some solutions: Ever since Firefox updated I am having trouble with font size consistency between the overall screen (message list, panel on the left), the size of incoming emails and the size of font in my replies. I have tried going to View – Font Size – Increase or Decrease. That changes the font of the overall screen including the message that is showing up in the bottom panel. But it doesn’t necessarily change the font size of other messages which is too small. I can open a message and then go to View at the top of the message to change the font size. But when I go to reply, the font size is still too small.

Is there some overall fix for this? Am I missing something?

The previous suggestions work for the home page, but don't change the content of incoming messages. They are just about readable but when I compile a new message or a reply the font in the editing window is very small. Changing the font in Tools>>Settings>>Composition>>HTML Style changes the font in the sent message but doesn't change the editing window

I have enlarged the font size on the main screen. Go to View, then Density, Click on Relaxed. Then Go To Font Size, Click on Increase Font Size till the font is what you want. I did this and even shut down and restarted and the Font remained the same.

My problem I still have is I cannot get the font type and size I like when I open the window to reply or write a new email