"Let’s set some things straight since these terms are often tossed around in the email world. You might wonder, “What’s the difference between zero-party and first-party data? Are there any others?” Worry not, email friend—we’ve got you covered.

• 
  Zero-party data is individual-level data given to you directly from your audience
• First-party data is individual-level data collected from your audience on your own channels
• Second-party data is individual-level data acquired from a trusted partner (someone else’s first-party data)
• Third-party data is aggregate data collected from one or more sources

Since that’s been cleared up, which ones do we like and which ones not as much? Zero and first-party data are your safest picks since you own that data. Second-party is another option as it comes from a trusted source that allows you to access and use it. Third-party is not as desirable due to its data integrity, which could cause problems with your email sender reputation down the road. With Yahoo and Gmail’s new deliverability rules being implemented in February 2024, if your brand sends over 5,000 emails daily, you’ll want to ensure that you maintain a spam complaint rate under 0.3%."