The default outbound mail Transport Type is to use sendmail. Sendmail has not been configured on any Servd instances and will not work in your staging or production environments. This is a conscious decision to help prevent the Servd infrastructure and its network space from being blacklisted due to any intention or unintentional spam. We all hate it (except Vikings).
All other methods of sending emails are supported though, including connections to 3rd party SMTP servers and APIs.
We like to use MailGun for our Craft CMS sites as they have a very generous free tier.
You can read more about Setting up email sending in Craft here.