$ man enterprise-mx-patterns

Enterprise = More Microsoft / Outlook

The pattern that enterprise companies (1,000+ employees) disproportionately use Microsoft 365 / Exchange / Outlook for email. SMBs and startups lean Google Workspace. Mid-market is mixed.

This pattern shapes your entire infrastructure strategy. If your ICP is enterprise, you need more Microsoft 365 sending infrastructure because most of your contacts are on Microsoft. If you only set up Google Workspace mailboxes and try to reach enterprise contacts, you're sending cross-provider for the majority of your list. Deliverability suffers.

Before I set up infrastructure for a new partner, I check the ICP. Enterprise ICP? I lean the provider split toward Microsoft 365 (60/40 or 70/30 Microsoft/Google). SMB ICP? I lean toward Google Workspace. I also validate this assumption with a test batch — run MX lookups on the first 500 contacts and check the actual distribution. Sometimes the assumption is wrong. The data tells me the real split.