@ClaireFromClare Well, when using Gmail, Google already has access to the content of all email you send and receive; while they do, have a privacy policy governing what they can do with that information, I think it's likely more than many of us are comfortable with. A good way to guard your privacy in Thunderbird (and other mail clients) is to make sure they do not fetch images, etc. embedded in email - I believe this is the default in Thunderbird. This is one of the main ways that email senders track you (eg. they can tell if you opened the mail if your mail client fetches the images in in it.) My understanding is that when you use the web interface to Gmail, Google does some caching and re-writing tricks to mitigate this, but fundamentally, when you use Gmail, you are giving up a lot of privacy to Google.
@ricci Thank you, that’s v interesting about opening the images. I understand about the gmail content, & use other email accounts for almost all correspondence, but am concerned about recent assertions that being “logged in” to gmail (as Thunderbird always is? & the gmail app on Android?) enables google to hoover up other data on the device. Does it?