Apple Mail - text wrap

With such a message open, at the menu bar go to View > Message.

If Plain Text Alternative is an available selection, this indicates the message was composed or sent with HTML format and/or RTF. Selecting this for such a received message should help but I'm not aware of a re-wrap feature which doesn't work on an HTML formatted message anyway. When a sender uses HTML for message composition, the sender controls the formatting.

When a sender uses HTML for message composition, the sender controls the formatting regardless which email client is used by the recipient.

HTML formatting was wrought upon the internet by Microsoft which came back to haunt and continues to haunt most Windoze users but mostly an inconvenience at times for Mac users. If HTML composition with email was banned tomorrow, the majority if not all problems experienced with the exchange of email would be eliminated.

Some email clients have a setting to automatically convert ALL HTML formatting to Plain Text for ALL received messages. Mail includes no such option since Microslop helped to enable the popularity of using HTML formatting.

There is a Terminal command which will do the same for Mail but ALL HTML received with any message will be converted to Plain Text.