Sorry to hear that! It's possible this is an issue with your email provider and not Tab Stash. Like most other tab-saving add-ons, Tab Stash saves tabs by remembering their URLs. What you're describing might happen if your email provider doesn't assign unique URLs to each email.

One way to test this is to open a specific email message, bookmark the page, and close the tab. Then use the bookmark to open your email again. If your email provider doesn't show that same email message, then it's unlikely to work with Tab Stash or any other tab-saving add-on, I'm afraid.

If, however, you DO get back to the same email message, then it's a problem with Tab Stash and I'd love to get a bug report on GitHub, so I can troubleshoot with you further.