I have a "1" next to my SENT folder, but there are obviously many more messages in the sent folder than just one. What is this? Why is if there? Is there something I can do to get rid of it?
I guess, this "1" indicates that there is "1 unread message in your SENT folder.
You could extend the view in Account list to see also the amount of 'all messages' in your folders:
Settings > Account list > scroll down to the last option 'Show per-folder "total" message counts > change to "Always" or "Auto".
