Emails sent from Acquia's mail server may be rejected when a Sender Policy Framework TXT has not been configured at your DNS provider. The misconception is to change your Sendmail path to *@acquia.com as this is where the mail is originating from. Using an email with @acquia.com indicates that these emails are being sent on behalf of that email address. This is a misrepresentation of your relationship with Acquia to the email's recipients which can be considered fraud!
If you are having issues with emails not being sent out from your registered domain, please see our documentation on Configuring SPF records for domains on Cloud Platform. Log into your DNS provider and add an SPF TXT record as the documentation states. If you are still having issues, please also look through Troubleshooting Drupal email issues.