MX records explained for cold email. What they are and why they matter

mx_explained · 2026-02-20 · 1,760 views

MX records are one of those DNS concepts that every cold emailer should understand even if they never configure one manually. Here's the plain English version.

What MX records are. MX stands for Mail Exchange. An MX record is a DNS entry that tells the internet where to deliver email for your domain. When someone replies to your cold email sent from john@yourdomain.com, the receiving server looks up the MX records for yourdomain.com to figure out which mail server should receive that reply. Without correct MX records, replies to your cold emails literally have nowhere to go.

How they work with Google Workspace. If you use Google Workspace for your cold email inboxes (which most people on PuzzleInbox do), your MX records point to Google's mail servers. The standard Google Workspace MX records look like: ASPMX.L.GOOGLE.COM (priority 1), ALT1.ASPMX.L.GOOGLE.COM (priority 5), and so on. These tell the internet: "deliver all email for this domain to Google's servers."

How they work with Outlook 365. If you use Microsoft 365 Outlook inboxes, your MX records point to Microsoft's servers instead. The format is typically yourdomain-com.mail.protection.outlook.com.

Why they matter for cold email. If your MX records are wrong, two things break. First, you can't receive replies. Someone responds to your cold email and the reply bounces or disappears. You've burned a warm prospect. Second, incorrect MX records can cause SPF and DMARC alignment issues, which hurts your overall deliverability.

PuzzleInbox sets these up automatically. When you order inboxes from PuzzleInbox, MX records are configured as part of the DNS setup process. You don't need to touch them. But you should know how to verify they're correct using MXToolbox or your DNS provider's dashboard. Just look up your domain's MX records and confirm they point to the right mail servers for your inbox provider.

MX records are simple but foundational. Get them wrong and your entire cold email operation breaks at the most basic level: you can't receive the replies you're working so hard to generate.