Yes. With DH, there is a cluster of machines for a group of customers. Usernames for shell/ftp are spread across this cluster of machines. Thus, if one customer thinks of using "info" first for a shell/ftp username, no one else on the cluster can use "info" for an shell/ftp username after that.
If you simply need mail sent to "info@yourdomain", then sent up a mailbox and have the address set to "info@yourdomain", or you can setup an ftp/shell user and then when you add the address "info@yourdomain" specify that mail should be delivered to the ftp/shell user.
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