Sometimes your emails might not show accurately as 'open' on your inspection details page. You might see a client email that hasn't been opened even though you know they have viewed the report. Each one of these emails has it's own unique ID, so if the agent decided to forward their email to the client who opened that email (not the original one sent to them), the email would have a different ID and would not register as the client opening their own email.
On the other hand, an email might show as 'open' and you assume the client has already seen the email even though they haven't. In this case, if your client or agent has a CC email, the IDs will be the same and will show your client having opened it when only their CC email did.
If you click into the email, you can see a more in-depth look, including when the email was delivered, when it was opened, and by which person (if two or more parties were included).