Every domain's MX records say who actually accepts its mail. That single fact, looked up before you send, changes how a campaign should be built.

Why the provider matters

  • Google Workspace weighs engagement heavily. Low open rates compound fast.
  • Microsoft 365 is stricter on authentication and link reputation.
  • Free consumer mailboxes (Gmail, Yahoo, Outlook.com) usually mean a sole trader, which is a different message entirely from a corporate contact.
  • Self-hosted and regional providers often have the loosest filtering and the highest reply rates.

Split before you send

Sending the same volume at the same time to every provider is what gets a domain flagged. Splitting by provider lets you warm each one at its own pace and see which is actually replying.

The business/consumer split

This is the most commercially useful cut. If you sell to companies, the free-mailbox segment is usually a different product conversation — and sometimes not a prospect at all. Knowing that before you write saves the sequence.