First, my version:
$ zmcontrol -v
Release 7.1.3_GA_3346.RHEL5_64_20110928134534 CentOS5_64 NETWORK edition.
I'm trying to set an infrequently used postfix parameter using zmlocalconfig. The parameter is "sender_dependent_relayhost_maps"

I set the parameter, and verify that it has been set:
$ zmlocalconfig -e postfix_sender_dependent_relayhost_maps=hash:/opt/zimbra/postfix/conf/sender_dependent_relayhost_map

$ zmlocalconfig postfix_sender_dependent_relayhost_maps
postfix_sender_dependent_relayhost_maps = hash:/opt/zimbra/postfix/conf/sender_dependent_relayhost_map
But when I reload the mta, postfix doesn't pick up the changes:
$ zmmtactl reload
Rewriting configuration files...done.
postfix/postfix-script: refreshing the Postfix mail system
Stopping saslauthd...done.
Starting saslauthd...done.

$ postconf sender_dependent_relayhost_maps
sender_dependent_relayhost_maps =
Has anyone encountered this problem before, or would be able to point me at some documentation that I may have missed while googling?