iRedMail version (check /etc/iredmail-release)
==>  0.9.9 MARIADB edition.

Deployed with iRedMail Easy or the downloadable installer?
==>  downloadable installer.

- Linux/BSD distribution name and version:
==> Debian 9.

Store mail accounts in which backend (LDAP/MySQL/PGSQL):
==> Mysql/MARIADB .

Web server (Apache or Nginx):
==> Nginx.

with Thunderbird add-on 'Lightning' SOGO domain address book sync properly it all shows all email ids which contains in Domain address book, but with outlook add-on CalDav Synchronizer it show test connection successful but Sogo domain address book email ids are not shown in contact list.

Also let me know how to allow modify permission to domain address book.

sogo logs

Oct 22 06:58:34 sogod [21064]: <0x0x5575eb13d090[SOGoActiveSyncDispatcher]> Sleeping 30 seconds while detecting changes for user xxx@domian.name in Ping...

#############################################################

nginx logs

2019/10/22 14:44:50 [error] 21095#21095: *29138 upstream timed out (110: Connection timed out) while reading response header from upstream, client:xxx.xxx.xxx.xxx,server: _, request: "POST /Microsoft-Server-ActiveSync?Cmd=Ping&User=abc@domain.name&DeviceId=74B422C7092B4C478CCE992583CD2597&DeviceType=WindowsOutlook15HTTP/1.1", upstream:"http://127.0.0.1:20000/SOGo/Microsoft-Server-ActiveSync?Cmd=Ping&User=abc@domain.name &DeviceId=74B422C7092B4C478CCE992583CD2597&DeviceType=WindowsOutlook15", host: "server hostname"

how to resolve this ?

Thanks
Sunil