Get-mailbox -resultsize unlimited

PSCredential credential = new PSCredential("Administrator", securePassword); // the password must be of type SecureString
        WSManConnectionInfo connectionInfo = new WSManConnectionInfo(connectTo,schemaURI, credential);
        connectionInfo.MaximumConnectionRedirectionCount = 5;
        connectionInfo.SkipCACheck = true;
        connectionInfo.SkipCNCheck = true;

        try
        {
            Runspace remoteRunspace = RunspaceFactory.CreateRunspace(connectionInfo);
            remoteRunspace.Open();
            var command = new Command("Get-mailbox");
            command.Parameters.Add("resultsize", "unlimited");
            var pipeline = remoteRunspace.CreatePipeline();
            pipeline.Commands.Add(command);
            // Execute the command
            var results = pipeline.Invoke();
            MessageBox.Show(results.Count.ToString());
            remoteRunspace.Dispose();
        }
        catch (Exception ex)
        {
            //Handle error
        }

Get-mailbox | select-object DisplayName, PrimarySmtpAddress, ForwardingAddress, alias, identity, legacyexchangeDN | where-object {$_.ForwardingAddress -ne $Null}