First of all, I love AquaMail. There's very little I would change about it.
About my only frustration with the app is on the main screen which lists the email accounts, I find the 3 subfolders for every account [Unsent messages], [Sent messages], and [Deleted messages] very distracting from what I care about -- seeing which accounts have new messages waiting.
I would like to have a setting where these subfolders could be completely hidden from the account list and only viewable once you tap on a given account. I realize they can be collapsed, but once you hit one of the email accounts, they are permanently viewable (until you select to collapse them again).
Alternatively, if these subfolders could be indented underneath the main account name, that might make things a little less cluttered.
Anyway, hope that makes sense!
Keep up the good work.