Having used Aquamail for over 3 years, and having read other users' confusion where to find settings that are under individual account settings, I came to the following conclusions:
1. For many people (and especially those who have only one e-mail account) it is not intuitive that they need to long-touch the account name to be able to change configurations that are otherwise unavailable in the general settings.
2. Even after so many years of using the app, I sometimes forget where some of the settings are.
3. Changing settings for a specific account requires getting out of that account to the account list, whereas changing the overall app settings can be done while I am in the Inbox of an account (or any other folder).
So, my suggestion is to make it possible to access individual account settings through the "Settings" option (and thus even from the message-list view). The way I see it to be simple would be to have just one option: "Configure individual account options" or "Configure per-account options", so that tapping on that option would open a menu with a list of the accounts, and tapping on one of those would be equivalent (a short-cut) to where you get after the long-touch on the account.
This would address all the concerns I outlined above, including #1, which affects number of support inquiries. And (hopefully) it shouldn't be too much work for you, Kostya.