What version of zcs are you running?
M2
What's in the file /opt/zimbra/cyrus-sasl/saslauthd.conf.in?
Actually it was in /opt/zimbra/cyrus-sasl-2.1.21.ZIMBRA/etc/saslauthd.conf.in zimbra_url: https://@@zimbra_server_hostname@@/service/soap/
zimbra_cert_file: /opt/zimbra/conf/smtpd.crt
zimbra_cert_check: off
Is your store (webmail) server on the same host as your mta?
Yes
Is your webmail server using http or https?
http