Close the Certificate Manager. Right-click the encrypted text file containing the message you'd like to read. Select "Open with" and click "TextPad" to open it in TextPad.

You can view a Text file in Command Prompt or PowerShell in Windows 11/10. You can view the entire content of TXT, a specific line, etc.

GoodReader A PDF and text file reader app, GoodReader, features a unique Reflow feature which has become its exclusive selling point.

Also, as Hints reader sudo points out, in Mail you can also save selected messages as Raw Message Source (instead of Rich Text), producing Unix-friendly mbox text files.

Need to edit a PDF document but don’t want to pay for the more expensive Adobe editors? You can add text to and sign a PDF with just the free Reader program.

Foxit Reader not only allows you to view your PDF files, but can also read them aloud using its text to speech feature. In order to configure this feature, follow the steps below.

Also, as Hints reader sudo points out, in Mail you can also save selected messages as Raw Message Source (instead of Rich Text), producing Unix-friendly mbox text files.