1. Login to the web interface as administrator through URL : https://quickpost.app/interface/root#/login
and administrator user name with password.
2. Click Settings icon> Domain Settings > Users.
3. Select an email account and Click on the three dots (blue) in the upper corner.
Click on the change password, admin is just an example here you have to select your desired user name.
4. Fill in the new password then confirm and click on Save.
5. You may try to log in the new email account now by using URL: https://quickpost.app/interface/root#/login
Note:
Only email administrator own the right to create/reset email account.
