Hello Mike,
thanks for your answer.
Don't know if it's related to the issue described above so I think it's not reasonable to create a new topic.
Before trying to switch to server-side synchronization I tried to use the E-Mail router first. I downloaded the latest version of Microsoft Dynamics CRM 2013 Email Router from official website. Then I started the Email Router Configuration Manager and added new deployment with appropriate settings (deployment type, CRM server location, access credentials and mail profiles).
But when I go to "Users, Queues, and Forward Mailboxes" tab and try to Load Data from existing deployment, i receive the following error message every time (obtained a full trace setting error log level to 3):
"#6188 - The Email Router service cannot connect to the Microsoft Dynamics CRM server or the Microsoft Dynamics CRM Online server to access user and queue information. Verify that the account that is used to run the Email Router service has sufficient permission to access the Microsoft Dynamics CRM server and that there are no connectivity problems. System.ArgumentNullException: Value cannot be null.
Parameter name: path1
at Microsoft.Crm.ServiceProxyCache`1.BuildServiceProxy(Uri serviceUrl, Credential credentials, Uri homeRealmUrl, String passportEnvironment, String onlineServiceEnvironment, IServiceConfiguration`1 serviceConfiguration)
at Microsoft.Crm.ServiceProxyCache`1.GetNewServiceProxy(Uri serviceUrl, Credential credentials, Uri homeRealmUrl, String passportEnvironment, String onlineServiceEnvironment)
at Microsoft.Crm.Tools.Email.Providers.OrganizationUrlCache.DiscoverOrganizationUrl(Uri discoveryServiceUrl, Credential credentials, String organizationName)
at System.Lazy`1.CreateValue()
at System.Lazy`1.LazyInitValue()
at Microsoft.Crm.Tools.Email.Providers.OrganizationUrlCache.GetOrganizationUrl(Uri discoveryServiceUrl, Credential credentials, String organizationName)
at Microsoft.Crm.Tools.Email.Providers.Utility.GetOrganizationServiceUrl(Uri discoveryUri, String authMode, String userName, String password)
at Microsoft.Crm.Tools.Email.Providers.Utility.GetCrmService(Uri discoveryUri, String authMode, String userName, String password)
at Microsoft.Crm.Tools.Email.Management.Deployment.GetCrmService(Deployment deployment)
at Microsoft.Crm.Tools.Email.Management.Deployment.LoadServerSetting()
at Microsoft.Crm.Tools.Email.Management.Deployment.Load(BackgroundWorker backgroundWorker)
at Microsoft.Crm.Tools.Email.Management.Configuration.UpdateAll(Boolean refreshDeployments, String configurationSettingsFilePath, String configurationFilePath)"
Tried some tips and tricks from the internets but with no luck. The error message never changed :(