More Info
Note. Care must be taken not to set up a loop between WorkgroupMail and the ISP. Will any messages that you return be sent back again to WorkgroupMail?
Detail
To ensure that messages sent to unknown mailboxes at your domain get sent up to the ISP, do thefollowing:
WorkgroupMail v8 and WorkgroupMail v7
Double click your Domain object in the WorkgroupMail Administrator. On the Unknown Recipients tab select the option to ‘Relay the Message if the Recipient is found in the Routing Table’.
Double click the Settings icon and select the Routing tab. Enter the general e-mail address for your domain as *@yourdomain.com. In the Server address you must put the IP address of your ISP’s SMTP server or the IP address of a public SMTP server which you can access.
Now, when a message is received for your domain, Workgroupmail first tries to find a local user mailbox to receive it. If it cannot find a local user then it treats the message as mail for an unknown recipient. The logic now states that unknown mail should be relayed if there is an entry in the routing table. So, the message is then sent to the internet via the specified SMTP server.
WorkgroupMail v6
Double click the ISP in the WorkgroupMail Administrator. Select the ‘Unknown Recipients’ tab and select the option ‘Relay unknown mail for these domains’. (NB in earlier versions of WorkgroupMail v6 this setting was located on the Address tab)