Mixpanel uses a tiered-ip system to prevent any of our IP's from getting listed as spam by major email providers, but there are certainly extra steps you can take on your end to improve delivery rates and avoid spam deliveries.
The best solution is to enable DKIM to allow Mixpanel to authenticate your Mixpanel emails. Setting up DKIM will improve deliverability and allow you to use your own domain rather than datadrivenemail.com; essentially, they add a layer of credibility to your emails, making them less likely to trigger spam filters or be bounced due to DMARC policy.
Once you’ve enabled DKIM, your emails will apply these changes once the DNS refreshes.
Aside from DKIM, much of what is marked spam is determined by the content of the email itself. There are some general guidelines that email providers use to determine whether something gets marked as spam.