Google Workspace vs Microsoft 365 for cold email (2026)

Google Workspace and Microsoft 365 landed on nearly identical entry-level pricing in 2026 after Microsoft’s July price increase — $7/user/month on an annual plan for either platform’s cheapest tier. The real difference for cold email is a Microsoft-specific new-tenant outbound block (error 5.7.708) with no self-service fix, and the two vendors sitting on very different timelines for retiring password-based SMTP auth.

Per-mailbox price, side by side

Both platforms’ entry-level, annual-commitment pricing now sits at $7/user/month (workspace.google.com/pricing and microsoft.com/microsoft-365/business, September 2026) — a genuine change from the historical gap between them, driven by Microsoft raising Business Basic from $6 to $7/user/month effective July 1, 2026:

Both vendors also sell month-to-month (no annual commitment) pricing at a markup over these figures, and both run promotional discounts for a limited number of seats/months at various points — check each vendor’s own pricing page for the current promo, since those change more often than the underlying list price.

Sending limits

Google Workspace caps external recipients at 2,000 per rolling 24-hour period per user (Google Workspace admin documentation, September 2026), with a separate 3,000/day cap on total unique recipients and a 500-external-recipient limit per individual message. Microsoft 365’s Exchange Online recipient rate limit is 10,000 recipients per mailbox per rolling 24-hour period (Microsoft Exchange Online service description, September 2026) (internal and external combined) — a separate, lower external-only limit was planned for April 2026 but was canceled indefinitely in January 2026 after customer pushback, so as of September 2026 the 10,000 combined figure is the operative ceiling. Both figures are rate limits enforced by the platform, not deliverability targets — sending anywhere near either ceiling on a cold-outbound domain will damage reputation long before the platform itself intervenes.

OAuth vs SMTP AUTH: very different timelines

Google Workspace already disabled basic username/password authentication for SMTP, IMAP, and POP as of May 2025 (Google Workspace admin documentation, September 2026) — OAuth 2.0 (or an app password, itself being phased toward OAuth) is required today, with no path back to a plain password for third-party SMTP senders. Microsoft has moved in the opposite direction: it originally planned to retire SMTP AUTH basic auth in 2025, pushed that to a phased rollout in early-to-mid 2026, and then delayed the retirement again — behavior is unchanged through December 2026, then disabled by default for existing tenants at the end of that month, with tenants created after December 2026 unable to use it at all (Microsoft Exchange Team blog, updated timeline, September 2026) and a final removal date not expected to be announced until the second half of 2027. In practice: if a cold-email tool or script connects via raw SMTP with a password today, that path is already closed on Google Workspace and still open, for now, on most existing Microsoft 365 tenants.

The 5.7.708 “tenant not trusted” block

A new or trial Microsoft 365 tenant is commonly assigned a low-reputation outbound IP pool by default (Microsoft 365 admin community reports, September 2026) as an anti-abuse measure, and the symptom is a bounce reading 550 5.7.708 Access denied, traffic not accepted from this IP. It hits legitimate new tenants, not just spam accounts — the block is based on the tenant’s newness and the shared IP pool it landed on, not on anything the sender did wrong. There is no documented tenant-side fix: a tenant admin has to confirm the mailbox has a fully provisioned Exchange Online license, then open a Microsoft support ticket specifically requesting an IP-reputation exception. Google Workspace has no directly equivalent hard block for new domains, though a brand-new domain on either platform is still subject to the same new-domain caution every major receiver applies — see why that makes warmup non-optional regardless of platform.

If you’re seeing this error on a new tenant, a full walkthrough of the fix path lives at /errors/5-7-708.

Deliverability reputation in 2026

Both platforms are large, well-regarded senders in their own right, and neither name alone determines whether your mail lands in the inbox — that comes down to your specific domain’s authentication (SPF, DKIM, DMARC), sending history, and list quality on top of whichever platform you’re on. The platform-specific risk worth planning around is asymmetric, though: a new Microsoft 365 tenant carries a real chance of hitting the 5.7.708 block described above, with a support-ticket-only fix and no predictable timeline, while a new Google Workspace domain has no equivalent hard block but still needs the same reputation-building ramp any new domain does on any provider.