When setting up dedicated cold email sending domains, you have two primary hosting options for the mailboxes: Google Workspace (Gmail) or Microsoft 365 (Outlook). Both are legitimate, professional email platforms used by hundreds of millions of businesses. They have different characteristics for cold email that affect inbox placement at major receiving servers.
Google Workspace for Cold Email
Google Workspace mailboxes benefit from Google's well-established SMTP server reputation. When cold emails sent from Google Workspace arrive at Outlook, Yahoo, or corporate Exchange servers, the sending IP is recognized as a legitimate Google infrastructure IP — not a new SMTP server. This provides a meaningful inbox placement advantage for new domains, particularly in the first 30 to 60 days before the domain itself has built significant reputation. Google Workspace plan pricing starts at $6 per user per month. Setup requires DNS verification and enabling Gmail SMTP access through Admin Console.
Microsoft 365 for Cold Email
Microsoft 365 mailboxes carry Microsoft's Exchange Online SMTP reputation, which Gmail and other receiving servers treat favorably. For campaigns where a large percentage of target prospects use Outlook or corporate Microsoft 365 accounts — common in enterprise, manufacturing, government, and financial services — M365 mailboxes sometimes achieve higher inbox placement at those specific destinations. Some cold email practitioners split their sending infrastructure between Google Workspace and Microsoft 365 to hedge against platform-specific filtering.
Which to Use
For most B2B cold email campaigns, Google Workspace is the simpler setup and provides reliable inbox placement across all major receiving servers. Microsoft 365 is worth adding when a significant portion of the target ICP uses corporate Outlook accounts. Omni uses both platforms across client sending infrastructure, managed through InboxKit for unified domain and mailbox management.