Because CanIt automatically generates user accounts, we need some way of determining which addresses actually exist. The default way we do this, with Setup->Verification Servers, is to run a preliminary SMTP session to your mail server where we try to ask for the requested recipient. It is expected that the mail server will only accept addresses that actually exist. This is not the case with many mail servers, however; they will accept mail for any address and then silently discard them later.
In order to get this functionality to work with MDaemon you need to:
- Navigate to the MDaemon GUI
- Select Security
- Select Security Settings
- Select Relay Control
- Check "SMTP RCPT must exist if it uses local domain"
- DO NOT CHECK the subsequent "...unless sent from a Trusted IP"
This can be seen from:
You can ensure delivery from the CanIt IPs by listing them from Security->Security Settings->Relay Control->Trusted IPs. If you do so, you must ensure you do not check the box in the list bullet above.
You can restrict delivery to your domains to only be allowed from the CanIt machine(s) with the IP Shield feature for MDaemon, discussed here:
The IPs used by Hosted CanIt are provided from My Domains->My Domains. If you have your own appliance, be sure to use whatever IP MDaemon sees it deliver from.