For me K9 nr. 1 for flash & lite check and manage mail on smartphone. It has no comparison with anything.
But I installed it to an elderly gentleman on his tablet because with gmail he went crazy to understand what has arrived what is sent what is attached. A delusion Gmail and I can't blame him.
But I do not know how to open folders in K9 to make the archive of the 4 emails that he believes to archive.
Can you help me?
Thanks.