The documentation portal is undergoing maintenance. During this period, you can't create any new user credentials. If you do, you'll need to recreate the user credential after the maintenance period ends.
When the Integration Service runs on Windows, you can enter one email address in the Workflow Manager. If you want to send email to multiple recipients, create a distribution list containing these addresses in the Personal Address Book in Microsoft Outlook. Enter the distribution list name as the recipient when configuring email.
For more information about working with a Personal Address Book, refer to Microsoft Outlook documentation.