Emails generated from actions on your site, aren't arriving for the intended recipients.
The cause for this issue is often because there is no DNS SPF record for the site's domain. To check for a DNS SPF record, run the following command against your domain:
dig www.mydomain.com txt
You'll need to confirm you've set up a DNS SPF record to authorise the Acquia mail servers and ensure that emails sent from your site aren't being blocked (to prevent sender address forgery). If your check shows no DNS SPF record, or a record that doesn't include a reference to Acquia, then see our guide on how to create the necessary DNS SPF record for the appropriate domain.
If you've confirmed you have a DNS SPF record for the appropriate domain, next steps are to check local email spam folders and local firewall or mail server configuration that could be preventing the email being delivered. If you're still unable to receive email sent from your site via the Acquia mail servers, contact Acquia Support for further assistance.
Also note that Acquia Cloud email is provided as a limited service, and which is described at About email in Acquia Cloud applications. We recommend using a third party email service if an unlimited and guaranteed service is required for business continuity.