If the Service reports a failure, wait another 5 minutes.
After this period, all containers should be accessible.
If the error remains, check if the connection to your storage was lost and try a reboot of your storage system.
In rare occassions, the ram consumption of the maildepot service can grow large and result in a slower processing and archiving of mails.
To solve this, it is possible to use the scheduled restart and set a time when the service will be automatically restarted by the appliance.