How to enlarge the view in mail?

With the e-mail in view

Use the 2 keyboard combination Command + to enlarge the Appearance of the message

Make even larger appearing use the same keyboard combo a second time

This will not change the actual Font Size in the message just the Appearance.

Should have mentioned, this will only happen on the e-mail In View

It does not apply to ALL E-mails

EDITED - me

What has not been discussed is increasing the font size shown in the message display and compose windows. That is in Mail Settings : Fonts & Colors : Message font. There, you not only have control over the font used, but its size as well. All of the other recommendations here are unnecessary when you do this.

j Is there also a way to do this in writing mode?

Choose a size that meets your needs in Mail > Preferences > Fonts and Colors > Message Font

You what to explore System Preferences >> Accessibility features

See if Zoom options would suit your needs

Welcome

There I am not 100% sure this will work

When you commence to compose the message, Change the Font Size to something larger

How the Recipient's e-mail client ( program ) renders this larger Font Size is totally out of your control

PRP_53 wrote:

Welcome

When you commence to compose the message, Change the Font Size to something larger

How the Recipient's e-mail client ( program ) renders this larger Font Size is totally out of your control

It is true some email clients have settings that let you ignore the font size set by senders, but Apple Mail in particular does not, so it will honor the larger font size you set in your New Message pane.

👍

Welcome