Do any services require a restart after changing Message Retry Interval?

I'm trying combat a "grey-list" issue by changing the Message Retry Interval to 15 min from 1 min. I did this change about 12 hours ago and I my test messages are still sitting in queue. I suspect a service restart is needed. Any ideas?

Set-TransportServer SAC79906MAILP01 -MessageRetryInterval 00:15:00

Thanks much! :-)