Why 'which is better?' is the wrong question
Every outbound team asks this question. The answer is: it depends on who you're emailing.
Google Workspace and Microsoft 365 are not interchangeable email providers. They have fundamentally different relationships with their own ecosystems. Gmail trusts other Gmail senders more. Outlook trusts other Microsoft senders more. This isn't a bug — it's how email authentication and reputation systems work.
So the real question isn't 'which is better?' — it's 'what does my recipient's inbox look like?'
Where Google Workspace wins
Google Workspace has a clear edge when your recipients use Gmail — which, as of 2026, is 70%+ of B2B email addresses for companies under 500 employees (source: Datanyze email provider market share).
Why: Google's spam filters apply less scrutiny to emails authenticated through their own infrastructure. A properly configured Google Workspace domain with SPF, DKIM, and DMARC passes Google's authentication checks natively. The sending reputation builds faster, and the warmup period is typically shorter (14–18 days vs 21–28 days for M365 sending to Gmail).
Google Workspace is also more forgiving of new domains. Microsoft 365 tends to be more aggressive about throttling new senders.
Where Microsoft 365 wins
Microsoft 365 wins when your recipients are on corporate Exchange or Outlook.com environments — which is the majority of enterprise companies (1,000+ employees).
Microsoft's SmartScreen filter trusts authenticated Microsoft senders more than third-party senders. If you're selling to Fortune 500 companies running Exchange, sending from M365 infrastructure gives you a measurable deliverability advantage.
M365 also tends to have slightly better deliverability to European corporate environments, where Exchange adoption is higher than in the US.
What the data shows
From our campaign data across both ESPs (2025–2026):
- Google Workspace → Gmail recipients: 89% inbox placement
- Google Workspace → Outlook recipients: 71% inbox placement
- Microsoft 365 → Outlook recipients: 84% inbox placement
- Microsoft 365 → Gmail recipients: 76% inbox placement
The best practice: run both
Set up 60% of your sending domains on Google Workspace and 40% on Microsoft 365. Then route emails based on the recipient's inbox provider.
This isn't just a nice-to-have — it's the single highest-leverage deliverability improvement most teams aren't making. You're not changing your copy, your targeting, or your volume. You're just sending from the right infrastructure.
Most outbound platforms send all emails from whichever ESP you connected. RocketSDR routes emails through the matching ESP automatically, based on the recipient's MX records. The lift is measurable within the first week.
Cost comparison (as of May 2026)
Google Workspace Business Starter: $7.20/user/month Microsoft 365 Business Basic: $6.00/user/month
For a setup with 20 mailboxes (12 Google Workspace, 8 M365): Google Workspace: $86.40/month Microsoft 365: $48.00/month Total: $134.40/month
This is the full cost of your sending infrastructure (excluding domains at $10–15/year each). For context, one booked meeting from outbound is typically worth $500–5,000 in pipeline. The infrastructure cost is rounding error.
Frequently asked questions
Is Gmail or Outlook better for cold email?
Gmail (via Google Workspace) has better deliverability to other Gmail users, who make up 70%+ of B2B inboxes. Outlook (via Microsoft 365) wins for corporate/enterprise recipients running Exchange. The best teams use both.
How many cold emails can I send per day from Gmail?
Google Workspace allows 2,000 emails/day per user, but for cold email, staying at 25–35/mailbox/day is the safe range. Going higher triggers spam detection even if you're under the technical limit.
Does Microsoft 365 have better deliverability than Google Workspace?
It depends on the recipient. M365 has better deliverability to other Microsoft/Exchange environments. Google Workspace has better deliverability to Gmail recipients. Neither is universally superior.
Should I use both Google Workspace and Microsoft 365?
Yes. A 60% Google Workspace / 40% Microsoft 365 split across your sending domains matches the inbox distribution of most B2B audiences and maximizes your blended deliverability.