postfix mail domains

[sseitz]

Regarding your second way (relaying) I never thought about adding the functionality of a filtering / backup relay gateway into a controlled shared host. In fact some kind of remote controlling a dedicated relay gateway in front of one ore more ispCP's would be really nice.
We're currently do similar with some heavily patched confixx hosts using xml-rpc to update a mail-relay cluster. This also allows us to do some handcrafted xml for special purposes (fallback MX, delivery to inhouse exchange, authenticate bangpath targets, etc.)
But by now, I'ld like to focus on your third topic. I assume this can be done without any caveats and customers can be told to remove all email addresses for a domain after they pointed MX to another host. This would be really transparent for the customers. If they cancel thirdpart service they could revert to normal behaviour by themselves just by moving MX back to their respective ispCP host and adding their email addresses again.
Another idea is to ignore the customers settings and regulary check for MX delegations to remove domains from the MTA if the MX doesn't point to it. This way the domains should also get added again if the MX points back to the MTA again. After a second thought, I do not prefer this, because customers will get confused if the reality differs from their shown settings. Alternatively the settings could be modified as well (removing email addresses), but this would be a oneway ticket.

cheeers,
Stephan