Aqua is connection-agnostic, it just uses system networking functions to connect -- and when there are errors, it's most likely due to something outside the app's control.
Now that being said...
Check Aqua settings -> network and make sure that "DNS" checkbox is enabled (checked)
Also "WiFi works" -- web browsing is one thing, and mail traffic is another. It's fairly common for public WiFi networks (airports, restaurants, etc) to only allow web browsing. You didn't say that those are public WiFi networks, but you also didn't say that they are not.
A debug log is welcome too.