Hi Debbie , thanks for your question! Yes, this is possible.
To opt-in to receive email notifications for a specific topic (thread), click the "Follow" button on the topic. You will receive notifications when new replies are added to the topic.
Note: If you are a moderator, by default you are already getting notifications for all posts. You can disable that in your notification settings by unchecking All postings in the Moderator section:
After you have disabled that setting, you will then just receive notifications for the topics or categories you have chosen to follow.
I hope that helps! Let me know if I can provide any additional assistance.