Help with writing mail please

The formatting capabilities of email (all email, not Apple's Mail app) are quite limited. The original standard describes plain text only, and text formatting is usually achieved as a hidden file attachment in either RTF or HTML format (alongside the original plain text message).

Mail clients usually have a setting to turn off formatting and display the message as the original plain text. So there's no guarantee that everyone will see the formatting that you spend time doing.

However, email text should auto-wrap in Mail. If this is not happening, then there may be some actual problem.

Menu choices Format -> Make Rich Text and Format -> Make Plain Text let you toggle back and forth between plain and rich text. Does the problem happen with both of them?

When you are in Rich Text mode, check the choices for Format -> Alignment, Format -> Indentation, and Format -> Alignment -> Writing Direction.

Does that solve it? If not, can you post a screenshot of the problem you see?

It sounds like he wants the column of text to
Be narrower. There's no simple way to format email like a print document, that I know of. However for legibility while writing email messages, just make the compose window smaller.

And however you see it when you compose it on the Mac is not necessarily how it's going to look when it is received on the other computers.