I view email in Thunderbird and have uBlock installed. Sadly the CSS Exfil addon for Firefox does not exist for Thunderbird but I view emails in plain text either way. I suppose I "miss out" on backgrounds, themes, animated GIFs. For me personally plain text is the way to go. Am I the only one using an email client these days? I prefer the client so I can keep my emails off the server and manage my own backups.