I have used AVG Free antivirus for many years now.  Recently, a new version - V7.0 - replaced the venerable V6.  V7 has new bells and whistles, including auto-update, but the new installation pops up balloons when working, and adds text to the outgoing and incoming email. Fortunately, these annoyances can be turned off.  Here's how.
1 Right-click the AVG icon in your system tray (bottom right corner of taskbar), and launch the AVG Control Center.
2

Right-click "Email Scanner" in the main pane, and click "Properties". 

3

In the "Properties" box, click, the "Configure" button and uncheck the two "Certify Mail" boxes.

4 Click the "OK" button.
5

Next, click the "Properties" button and clear the "Show notification icon" and "Show information window" boxes.

6

Click "OK" and then OK again. Minimize the AVG Control Centre.

7 You're done!