Most classified ad sites are setup to have people respond to your ad by email.
So it only makes sense to use a tracking email to receive replies that can be easily tracked and sorted.
Now when you place an ad, instead of adding your real email address, you use a unique tracking email created just for that ad.
Creating an email tracker is quite simple as shown below:
Copy the tracking email, go to your ad posting site and paste the tracking email into your ad description before submitting your ad
Once your ad goes live, you can review the activity reports to see the number of emails received. You can compare ads to see which ones receive the most email replies.