Google vs Microsoft vs SMTP

There are four kinds of sending infrastructure in cold email, and the choice is a trade between trust, cost and fragility. Google Workspace mailboxes inherit Google's IP reputation and are the default, but they cost roughly $7 per 1,000 emails through a reseller and Google has shown it will suspend them in waves. Microsoft 365 mailboxes are sold per domain at a lower cost per inbox, carry a different suspension profile and are throttled harder per mailbox. Private SMTP is three to five times cheaper per email, has no Google or Microsoft account to lose, and inherits whatever reputation its operator's IPs have earned. Dedicated IPs give control and full responsibility.

#The four types side by side

Prices: Premium Inboxes, Inboxkit, Primeforge, Hypertide, Scaledmail, Maildoso, Instantly, Infraforge. Cost per 1,000 is my arithmetic at 22 sending days a month and each vendor's own cap; the method is on Inbox & domain infrastructure.

#Google Workspace

The default for most cold emailers. Mail leaves Google's IPs, which have strong reputation, and Gmail-to-Gmail delivery is the most-cited reason for ESP matching.

• Limits. Google's documented ceiling is 2,000 messages per user per day; trial accounts get 500, and moving off trial needs $100 of cumulative payment and up to 75 days for limits to rise (Outboundsystem, a vendor blog summarising Google's docs). Cold senders treat 15–30 per day as the real limit; Scaledmail caps Google at 25 per mailbox.
• Cost. Retail Business Starter is about $7/user/month (EmailBison); resellers sell at $2.50–3.50.
• Fragility. EmailBison claims about 22% of high-volume new Google accounts were suspended within 90 days, versus under 9% on Microsoft. It does not publish its method, but the direction matches the autumn 2025 wave (Provider crackdowns).

#Microsoft 365 and Entra tenants

Microsoft's per-mailbox ceilings are high on paper: 10,000 recipients a day and 30 messages a minute. The binding constraints are elsewhere:

• Tenant external recipient rate limit (TERRL) scales with the number of licences; trial tenants are capped at 5,000 external recipients a day, and mail from default onmicrosoft.com domains is capped at 100 external recipients per organisation per day (Microsoft Learn).
• The per-mailbox 2,000 external-recipient limit Microsoft planned since 2024 was cancelled on 6 January 2026.
• Vendors sell Microsoft by the domain: Scaledmail $50 per domain for 25 mailboxes at 10/day each, Hypertide $25 per Entra domain with 25 inboxes, Inboxkit $30 per Azure tenant holding up to 100 mailboxes. Maildoso's comparison puts the safe rate on cheap Azure tenants at 2 emails per mailbox per day.

#Private SMTP

The vendor runs its own mail servers and IP pools. Maildoso sells mailboxes at $0.49–$2.50 with a 15-per-day cap and "IP rotation"; Mailforge runs a shared pool it compares to how Gmail distributes users "among millions of businesses" (Mailforge); Smartlead resells Mailreef and AeroSend SMTP at $3.99–4.20; and in August 2026 Instantly launched AirMail on "owned, aged IPs", $4 per account, 20 per day.

The case for SMTP is cost and control: no Google tenant to suspend and roughly $1.50–4.30 per 1,000 sends. The case against: receiving filters judge the IP and domain, and a shared pool's reputation is set by its worst customers. Gmail and Outlook recipients see mail from a small ESP's IP range, not from Google or Microsoft — so the ESP-matching advantage disappears.

#Dedicated IPs

Infraforge sells them at $99 per IP per quarter; Mission Inbox advertises one dedicated IP per mailbox. A dedicated IP isolates you from neighbours but needs consistent volume to build reputation; at cold-email volumes per IP (hundreds a day) it rarely accumulates enough history. Useful for large senders with stable volume; a liability for small ones.

#ESP matching: real effect or marketing?

The pitch: send Gmail prospects from Google mailboxes and Outlook prospects from Microsoft. EmailBison claims matched sends land 87–92% in the inbox versus 74–81% cross-provider. A September 2026 analysis by Getle.ad of 34,973 sends found the opposite: "A properly authenticated Google Workspace sender reaches a Microsoft inbox at the same rate as a native Microsoft sender". Both are vendor content. Matching needs a recipient MX lookup and an inbox pool per provider — cheap to build, so it is a feature, not a moat. Detail on ESP matching.

#How agencies actually blend

Scaledmail's own worked example — 2,000 emails a day across Google, Microsoft and SMTP for about $654 a month — is typical of the pitch: put Google on the highest-value prospects, Microsoft domain packs on volume, SMTP on cheap testing and re-sends. After October 2025 the Salesforge newsletter's advice was blunt: "Don't rely exclusively on a single provider like Gmail or Outlook".

#What this means for an entrant

• Support all three types from day one. Google OAuth, Microsoft Graph/OAuth and raw SMTP/IMAP. A blended stack is the norm; a Google-first sequencer loses agencies after the next wave. See Sending architecture and OAuth verification and the end of basic auth.
• Make provider-aware routing the default. Per-provider daily caps, recipient MX detection, and automatic rerouting when a tenant throttles are cheap to build and visibly protective.
• Price on cost per 1,000 sends, not per inbox. The spread between $1.50 and $19 per 1,000 is where customers feel the pain; a sequencer that shows it, and optimises the blend, is selling something Instantly does not show.
• Do not own IPs early. Dedicated IPs and private SMTP are an operations business with abuse-desk overhead. Resell first; see Infrastructure strategy: build or partner.
• EU angle. Every vendor reviewed sells US IPs as a feature. For EU senders (Julian's home market) the legal question is about consent, not hosting — see Germany and GDPR and ePrivacy — but an EU-hosted SMTP option is unclaimed ground.