DANGER DANGER WILL ROBINSON!
The default setup PERMANENTLY deletes emails on the server when the trash folder is purged! Unless a user specifically happens upon the setting to change this to "hide local, do not delete on server", this DESTRUCTIVE behavior happens by default and without warning. I told a friend of mine about this app before I stumbled across this deadly default behavior, and she immediately purged the trash folder on her phone and thus lost EVERY email on the server before she could download in on her PC (primary email client). Fortunately, the emails were all spam, but it could have been a disaster instead.
Other email clients do NOT EVERY delete from the server by default and thus must default to NEVER delete mail on the server, so new users would likely assume that this app would also take the most conservative approach by default. NO DELETE ON SERVER is a critical required behavior for many users so PLEASE add this as a choice AND default to it. Hiding the mail locally is not secure and slows the device down, so that is not a good workaround for many.
Hope this helps.
I greatly appreciate your efforts and careful consideration of user feedback.