I know what was in the update and what wasn't. Nice for RR to put the blame on someone else.
For RR, Aqua Mail's preset is to use IMAP, which by design allows simultaneous access to a mail account from several devices or mail apps.
But please check: long press on the account -> options and folders -> you should see "IMAP options" and not "POP3 options" (indicating the account is set up to use IMAP and not POP3).
Now if the account is set up in Outlook as POP3 -- well, it should not cause any errors either, in theory, but POP3 is not designed for simultaneous access from multiple apps. Most can deal just fine though, but since your account is not --
-- I would investigate switching how it's set up in Outlook from POP3 to IMAP.
If both apps are set up to use IMAP and not POP3 already, well...