Logs from web console:

[Error] this.to.forEach is not a function. (In 'this.to.forEach(function(e,t,s){e.email&&0<e.email.indexOf("@")&&(s[t].email=punycode.toUnicode(e.email))})', 'this.to.forEach' is undefined)
https://REDACTED/SOGo.woa/WebServerResources/js/Mailer.services.js:1

(anonymous function) (angular.min.js:100:195)
$digest (angular.min.js:154)
(anonymous function) (angular.min.js:156:275)
(anonymous function) (angular.min.js:168:233)
(anonymous function) (angular.min.js:52:242)

Below the configuration file:

{
SOGoCalendarDefaultRoles = (
PublicViewer,
ConfidentialDAndTViewer,
PrivateDAndTViewer
);

WOWorkersCount = "60";
SOGoACLsSendEMailNotifications = YES;
SOGoAppointmentSendEMailNotifications = YES;
SOGoDraftsFolderName = "Drafts";
SOGoJunkFolderName= "Junk";
SOGoMailDomain = "sogo.local";
SOGoEnableEMailAlarms = YES;
SOGoFoldersSendEMailNotifications = YES;
SOGoForwardEnabled = YES;

SOGoUIAdditionalJSFiles = (
  js/theme.js,
  js/custom-sogo.js
);

SOGoEnablePublicAccess = YES;

// Multi-domain setup
// Domains are isolated, you can define visibility options here.
// Example:

// SOGoDomainsVisibility = (
//  (domain1.tld, domain5.tld),
//  (domain3.tld, domain2.tld)
// );

// self-signed is not trusted anymore
WOPort = "0.0.0.0:20000";
SOGoMemcachedHost = "memcached";

SOGoLanguage = French;
SOGoTimeZone = Europe/Paris;
SOGoMailAuxiliaryUserAccountsEnabled = YES;
SOGoMailCustomFromEnabled = YES;
SOGoMailingMechanism = smtp;
SOGoSMTPAuthenticationType = plain;

SxVMemLimit = 384;

SOGoMaximumPingInterval = 3540;

SOGoInternalSyncInterval = 45;
SOGoMaximumSyncInterval = 3540;

// 100 seems to break some Android clients
//SOGoMaximumSyncWindowSize = 99;
// This should do the trick for Outlook 2016
SOGoMaximumSyncResponseSize = 512;

WOWatchDogRequestTimeout = 30;
WOListenQueueSize = 16;
WONoDetach = YES;

SOGoIMAPAclConformsToIMAPExt = Yes;
SOGoPageTitle = "SOGo";
SOGoFirstDayOfWeek = "1";
SOGoFirstWeekOfYear = "First4DayWeek";

SOGoSieveFolderEncoding = "UTF-8";
SOGoPasswordChangeEnabled = NO;
SOGoSentFolderName = "Sent";
SOGoMailShowSubscribedFoldersOnly = NO;
NGImap4ConnectionStringSeparator = "/";
SOGoSieveScriptsEnabled = YES;
SOGoTrashFolderName = "Trash";
SOGoVacationEnabled = YES;

SOGoCacheCleanupInterval = 900;
SOGoMaximumFailedLoginCount = 10;
SOGoMaximumFailedLoginInterval = 900;
SOGoFailedLoginBlockInterval = 900;

GCSChannelCollectionTimer = 60;
GCSChannelExpireAge = 60;

MySQL4Encoding = "utf8mb4";

//SOGoDebugRequests = YES;
//SoDebugBaseURL = YES;
//ImapDebugEnabled = YES;
//SOGoEASDebugEnabled = YES;
//LDAPDebugEnabled = YES;
//PGDebugEnabled = YES;
//MySQL4DebugEnabled = YES;
//SOGoUIxDebugEnabled = YES;
//WODontZipResponse = YES;
WOLogFile = "/dev/sogo_log";
}