You can easily exclude properties that are under offer from your auto fed property panels.

To do so, starting in the email editor, click on the relevant property panel to make it active.
The auto-feed toggle should be switched on.

From here:

• Click the Define Properties button.
• Within the pop-up, stay on the Basic tab.
• At the bottom of this tab, tick Exclude properties marked as under offer.
• Click Update.

Note: This effects this panel only, so if you want to exclude them from other property panels in your email, just repeat this process.