Sorry to hear your are having problems with Mavericks...
Try rebuilding your mail. Launch Mail.
Select the sent mailbox on the left.
From the Mail menu bar click Mailbox > Rebuild
That can take a few minutes.
As for scanning. There's a workaround ..
Launch Image Capture located in your Applications folder.
Connect the scanner to your Mac whether Wi-Fi or USB.
Click the very small black box bottom left side of the Image Capture window.
You'll see this pop up menu: Connecting this (device) opens:
You can select a default app to scan (Image Capture) and select a folder from the Import To pop up menu on the right to save scanned files to.
If you need help with the Image Capture software, click Help from the Image Capture menu bar.
Mac Basics: Using a scanner