I have the following situation: a domain xy.org which has users on two servers: one exchange server (B) and one postfix(A). in front of that two systems is another portal-host, which cannot distinguish between mails for users on system A or on system B and therefor send everything to A.
users will get moved from exchange to postfix in batches and i would like to do the following: postfix is the leading system and will receive all mails. if a user is not already on postfix (and would generate a "User unknown in virtual alias table") then the mail should be sent to the exchange host. i know this is not ideal, because of the possibility of backscatter. this should not happen as the portalhost filters unknown recipients from external. Server A would only get valid recipients either living on A or B. from internal (without the filter on : if a user is unknown on A, mail is/should be forwarded to B and if the the user is not know there an NDR would be generated for internal mails. i thought it would be possible to use fallback_transport, but this does not work with virtual_alias_maps. below is an excerpt from my main.cf 10.10.10.10 would be the exchange server. ... virtual_alias_domains = /etc/postfix/virtual_domains virtual_alias_maps = hash:/etc/postfix/virtual, hash:/etc/aliases ... fallback_transport=smtp:[10.10.10.10] local_recipient_maps= ... how should i work around that? yours josef
