The causes of the error is it might occur if the hackers have used your Exchange Servers to send spam emails. This results in the fill up of Badmail folder with the messages which becomes impossible to handle by your server. Also, the messages cannot be reversed as the address is not a valid one.
For the resolution of the error, do all the following steps:
At First, Stop the Simple Mail Transfer Protocol (SMTP) service. To stop this service, follow these steps:
Go to the Computer Management, double click on the Services and Applications section, & select Services.
Then, in the right pane of the Services, click on SMTP & on the shortcut menu, click Stop.
Thereafter, got to the Badmail folder & delete all the messages from it. The location of the Badmail folder is Exchsrvr\Mailroot\vsi 1 folder.
After deleting the messages, start the System Manager, locate that server which was used to send the bad emails & then double click on Protocols.
Then, double click on SMTP node. You will find virtual SMTP server, right click on it & click Properties.
5. After that configure the Exchange Server in such a way that it sends only SMTP mails which is originated from your network. To acquire this, you need to do the following steps:
Select the Access tab & go to Relay.
In Relay Section, select the checkbox showing 'Allow all computers which successfully authenticate to relay'. Selecting this checkbox makes the SMTP emails to relay through the virtual server from your internal server.
After that select the checkbox of Only the list Below. The list which follows is left empty frequently, apart from the situations while you wish to allow the computer external to be able to send the SMTP mail through the server. And, if you want to allow the computer external to your network yourself, click on Add, & configure the correct IP range or domain name.
Then, in the dialog box of Relay Restriction, click on OK.
In order to mount the databases, go through these steps:
Double click on the Storage group lying under your server.
Thereafter, right click on the dismounted store, & then select Mount Store from the menu.