If you want to allocate more space for your postmaster email account or other email accounts, you can follow the steps below to change it from your hosting control panel.
1. Login to your hosting control panel
2. Click on 'Emails'
3. Click on the Manage Users & Quotas under the actions option.
4. Click on 'Quota Manager'
5. Select the email account and fill the size that you want to allocate and then click on 'Update':