Question about Outlook on an IPhone

I had to completely restore my phone for whatever reason. Now my outlook email has 600 messages in the in box. As I delete the old ones it will immediately start down loading another 2-300 older messages. These are all messages I've deleted from the trash folder.

Why are these continuing to be downloaded after being deleted from both inbox and trash folder?

Is there another way to delete from the inbox rather other than having to tap on each one? Like the trash box has the option to delete all, does the inbox have a more efficient way?

I'm sure I'll attract theiphone-stopped reading there element.