Changing the suffix will have no effect on the file. The text suffix (in
fact most suffixes) is fairly meaningless in Linux. You can open just about
any file in a text editor. Again, right-click and choose, open with and
choose your text editor, Kate or Gedit. With html email you will get the
html formatting codes, but the text will be intact. With text email, you
won't even get that. Whether it is .*eml or *.txt will be irrelevant.