There is 2 option to reset user password. You may reset via admin access (postmaster) or user account.
VIA USER ACCOUNT
1. Login to webmail (https://mail.example.com)
2. Click Setting – Account - Change Password
3. Please enter your "Old password", “New Password” and“Confirm Password”
4. Click on Save
VIA ADMIN ACCOUNT (POSTMASTER)
1.Login to webmail (https://mail.example.com)
2. Click Domain Setting – Accounts - Double clicks user account
3. Click "..." button and Click Change Password
4. Please enter your “New Password” and “Confirm Password”.
5. Click Save.