Hello,
Your Outlook is configured to upload sent mail to a different folder than whatever's used by web mail...
... and AquaMail automatically discovered the Sent folder in web mail (on your IMAP server, to be more exact), but of course knows nothing about Outlook.
Two possible solutions:
- Right solution: change your Outlook account setting so it uploads sent messages to the one and same Sent folder that web mail uses (and the IMAP server reports as being "the" Sent folder).
- Um, "less right" solution: in AquaMail, long press the account, then Options and Folders -> Folders, find Outlook's Sent folder, tap it, choose "Sync with [Sent]".