|"when I open email attachments......."|
Do these attachments have a .txt file extension?
As Ewen pointed out, emails can't be read with notepad, but attachments can provided they have an appropriate file extension, e.g. txt, log, etc. Some email programs won't allow you to open files with certain file extensions, due to the possibility of those files being infected. To get around this, some people will change the file extension before attaching it to an email. Of course, unless you know what the original extension was, you won't know what program to open it with.
Check the file extension and if it's something other than txt, let us know so we can advise you what program to use.
Please let us know if you found someone's advice to be helpful.