zmlocalconfig -s | grep lmtp zmlocalconfig -e postfix_lmtp_destination_concurrency_limit=20 zmprov -l gs `zmhostname` | grep zimbraLmtpNumThreads zmprov ms `zmhostname` zimbraLmtpNumThreads 40 https://wiki.zimbra.com/wiki/Performance_Tuning_Guidelines_for_Large_Deployments