You can sign out of your Business Mail mailbox by simply following the below-mentioned steps:
1) Click on the Settings icon at the top-right corner
2) Navigate to the option of Logout
3) Select the mailbox you wish to logout from in the Preferences for field at the top.
4) Click on Logout of this account on the bottom
5) Confirm your choice by clicking on the button Logout
6) Once confirmed, you'll be logged out of the account!
Feel free to reach out to us at support@onlydomains.com for any queries regarding this, we'll be happy to help you!