======== Required information ====
- iRedMail version (check /etc/iredmail-release):  0.9.8 MARIADB edition.
- Linux/BSD distribution name and version: Ubuntu 18.04
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): Mysql
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

After a default iRedmail installation with SOGO selected I am facing this problem.

Mail portion of SOGO works fine. Trying to access Calendar or address book results to a white page.

I have noticed that Memcached fails to start:
   Loaded: loaded (/lib/systemd/system/memcached.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Fri 2018-06-22 18:07:26 CEST; 11s ago
     Docs: man:memcached(1)
  Process: 10433 ExecStart=/usr/share/memcached/scripts/systemd-memcached-wrapper /etc/memcached.conf (code=exited, status=64)
Main PID: 10433 (code=exited, status=64)

Jun 22 18:07:26 webserver systemd[1]: memcached.service: Main process exited, code=exited, status=64/n/a
Jun 22 18:07:26 webserver systemd[1]: memcached.service: Failed with result 'exit-code'.
Jun 22 18:07:26 webserver systemd[1]: memcached.service: Service hold-off time over, scheduling restart.
Jun 22 18:07:26 webserver systemd[1]: memcached.service: Scheduled restart job, restart counter is at 6.
Jun 22 18:07:26 webserver systemd[1]: Stopped memcached daemon.
Jun 22 18:07:26 webserver systemd[1]: memcached.service: Start request repeated too quickly.
Jun 22 18:07:26 webserver systemd[1]: memcached.service: Failed with result 'exit-code'.
Jun 22 18:07:26 webserver systemd[1]: Failed to start memcached daemon.

This is the verbose log of SOGO

https://pastebin.com/6gyzaUc8

There is nothing relevant  in nginx logs