The Black Berry 10 OS will auto configure your sent folder for synchronization, however if you're using it with Outlook, you may need force Outlook to Synchronize folders to get things working properly with your Black Berry 10 device.
This is even more obvious on mobile devices like the i Phone.
We highly recommend creating a "Sent Archive" folder on your primary computer.
Every 6 months or 1 year, drag and drop the year-old Sent items into the Sent Archive.
Since they're messages from a year ago, you likely won't need to refer to them from your i Phone or other mobile device, but you will still have access to them from your home or work computer (whichever you do the archiving on).
One of your devices must have at least one of those directions incorrectly configured - fix the configuration and your Sent mail will remain synced across all of your devices.You can find the Sent mail folder configuration using the following directions.