The DNS mx record is what controls which email server is responsible for receiving your domains email. You can edit your MX records by clicking on “Hosts/Redirects” in our customer portal then clicking “Modify” on the root hostname for your domain (i.e. your domain.com). Towards the bottom of this page you’ll see “Mail Options” dialog.
By default, No-IP sets up the host mail.yourdomain.com to handle mail for your domain. You’ll need to have a mail server running on that host. Alternatively, you may update your mx records to point to a mail server/provider that is configured to receive mail for your domain.
If you do not want the hassle of configuring and maintaining your own mail server consider our IMAP/POP3 Managed mail service.