Office 365: Sent stored twice

[marbetschar]

What Happened

Since #607 sent mails are copied to the Sent folder. However, in Office 365 the mail appears twice in the Sent folder (Screenshot of Sent folder in Office 365 web interface):

Expected Behavior

The sent mail should only be stored once in the Sent folder.

Steps to Reproduce

1. Configure your Office 365 mail account in System Settings > Online Acconts
2. Start Evolution and let it detect all well known folders (should be fixed once Configuring well known folder URIs switchboard-plug-onlineaccounts#192 is merged)
3. Close Evolution
4. Start elementary Mail and verify the Sent folder is rendered using the proper icon
5. Send an email from your Office 365 account
6. You'll notice the sent mail will be stored twice in your Office 365 account

Platform Information

elementary OS 6 Daily.