Stopping mail relay using the percent % symbol
Allowing relay through your server using the percent % symbol can lead to being blacklisted
This problem can occur if the main mail server is accepting mail for relay from a fallback server. The main mail server should not need to do this, as when it accepts mail from the fallback server, it does not need to be passed on any further.
Consequently, the "Friendly hosts" list should be amended accordingly on the main mail server to prevent the fallback server from relaying
This can be done in the "Accept mail for relay from these friendly hosts" section of the “SMTP Security” settings. The IP addresses of the machines that you do not want to relay for should be entered at the start of the list, proceeded by a "!" symbol.
Wildcards can still be used, as the list works from top to bottom. For example, if you wish to block IP address 188.8.131.52, but want to allow all other 12.34.56.* IP addresses to relay, the list would look as follows:
See these other knowledge base documents:
Last revised 2006-9-29