Absolutely! Thundermail offers a Webmail client, though it is currently in early alpha.
You can access your account's Webmail any time at webmail.thundermail.com.
Development has been very active, with changes happening all the time! If you would like to see what's being worked on, you can check out the Stormbox repository on GitHub.
If you have thoughts on how to improve Webmail, please visit the Webmail section of Thundermail Ideas, our feature request board. Take a look to see if your idea is already there to upvote and comment on. If it doesn't exist yet, click the "Share Idea" button to let us know what you'd like to see in the future!