It is not possible to retrieve the password of the firstname.lastname@example.org automatically.
If necessary, you can access the Email Control Panel and change the password of each single account.
To access the Email Management section you need to enter the ‘Domain name’ (without www) as the Postmaster Username and then the current password of the postmaster account.
Once you have accessed the properties of each single account, you can specify a new password, which will be activated as soon as you select the Update Account button.
For further information on how to change the password, use the relevant video guide.
For the PEC Email Accounts of the domain follow the instructions available here.