If you really want no relayhost for a list of senders, this is not easily done with Postfix. sender_dependent_relayhost_maps was designed to do the exact opposite: specify a relayhost for a list of senders.
If the sender list is REALLY small, you could use the pcre built-in negation operator: /etc/postfix/main.cf: relayhost = sender_dependent_relayhost_maps = pcre:/etc/postfix/sender_relay.pcre /etc/postfix/sender_relay.pcre: if !/[EMAIL PROTECTED]/ if !/[EMAIL PROTECTED]/ /./ [my.isp.com] endif endif This sends mail from everyone but a few to [my.isp.com], but this approach becomes unwieldy if you need to specify many senders. Of course we could introduce a hack where a special lookup result of "NONE" (or some other magic string) means don't use a relayhost. Postfix would then look like this: /etc/postfix/main.cf: relayhost = sender_dependent_relayhost_maps = hash:/etc/postfix/sender_relay static:[my.isp.com] /etc/postfix/sender_relay: [EMAIL PROTECTED] none [EMAIL PROTECTED] none which is much cleaner. Introducing "NONE" (or whatever) requires a source code change. It also will raise expectations: people will try to use it in other tables and be disappointed that it does not work there, just like you tried to use "smtp:" in a place where Postfix expects "host" or "host:port". Wietse