Is there a reason for an email showing clicked but not opened

[#1]

For a conversation template, the email includes no images and a hyperlink as the CTA. The data is showing clicked but not opened. Would you know why this occurred? 

[#2]

Hi @ejohnson0832,

This can happen when a recipient's inbox has a firewall in place which scans all links within an email. Because of the scanning, the links will register as clicked, while the email itself has never been opened. 

Thanks,
Jenny