I just setup Thunderbird on my computer and since i was losing emails I wanted to keep as the older ones were deleted from my gmail account, I set up the account on Thunderbird as a pop 3 account and over 1200 emails were downloaded. I want mark them all read now before any more are downloaded , then as I have time go through them and delete those I don't want to keep as it is now, I have to select each one wait for it to be marked as read then select the next. I want to select all of them and mark them as read, but the only options i see when I select multiple messages are archive and delete.