Hello,
If it is GDM it does not have a password every user which is member of the GDM ( if the GDM has been created with CCA) has option to reach it when he/she is in their own mailbox and select option 9.
If you want to define new members just add them to the group in CCA or you may use the CUE web gui usually at 10.1.10.1 if it is the default one and add members to the GSM.
If this is a personal mailbox but you use it as GDM then just change the password for that user could be done from both CCA and CME webgui.
HTH,
Alex
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