Increase Font Size on External Display / Monitor

The main mechanism for doing what you are asking for across ALL Applications is to change SCALED, which is NOT the same as changing screen resolution.

When you adjust SCALED, the display is still runs at its 'natural' maximum resolution. Graphics will be displayed at that maximum resolution.

When text is being rendered for display, it is drawn MUCH larger, by a factor, such as 1.2, 1.5, or 2x the natural resolution. it appears larger, but has excellent smooth edges and gradual transitions. The text remains sharp and crisp and never 'grainy'.

if you want to increase the font used most often in Mail:

mail > preferences > Fonts & Colors...

you can select a default font for

the message LIST,

for viewing messages and

for fixed-width text

[personally:

my message list uses Lucida Grande 14 point

messages use Helvetica 18 point

fixed-with uses Menlo regular 18 point ]

There are also ways to adjust the size of both text and Icons on the Desktop.

I don't recall the details, but could re-derive it if you need it. Just post back for help with that.

--------

f you are Vision impaired, there is a whole host of assistance built into MacOS, ready to be activated in

system preferences > accessibility

If you want to increase the font size only in safari:

Safari > preferences > Advanced ...

... [√] Never use font sizes smaller that nnn points high

[personally, I have that set to 16 point]