The four inbox types, and what they actually cost you
Every inbox you use for cold email falls into one of four categories. The differences aren't subtle. They determine your deliverability ceiling before you write a single word of copy.
Metric | Google Workspace | Outlook Premium | Outlook Normal | Private SMTP |
|---|---|---|---|---|
Cost/inbox | $2.99 | $0.40 | $0.30 | $0.50 |
Inboxes/domain | 5 | 100 | 100 | 5 |
Cold sends/day | 18–22 | 8–10 | 3–5 | 11–14 |
Deliverability rank | #1 Best | #2 Excellent | #3 Good | #4 Variable |
vs. Google baseline | Baseline | ~15–20% worse | ~20–25% worse | ~35–50% worse |
Warmup time | 2–3 weeks | 3–5 days | 3–5 days | 3–4 weeks+ |
Inboxes for $500 | 175 | 1,300 | 1,800 | 1,000 |
Cold sends/day for $500 | 3,500 | 10,000 | 9,000 | 12,000 |
Google Workspace is the gold standard. Bulletproof IP reputation, Google-owned infrastructure, and the highest spam filter intelligence of any option. The tradeoff: $2.99/inbox with 5 inboxes per domain. For high-value ICP outreach, this is the only choice that makes sense.
Outlook comes in two flavors most people conflate. Premium (100 inboxes/domain, $0.40/inbox) is built for high-volume trusted sends. Normal ($0.30/inbox) is cheaper but your deliverability takes a meaningful hit, 20–25% worse than Google baseline. Both run on Microsoft Azure with bulletproof IP reputation, but neither should be used with an ESP in the "From" field. That's a fast track to spam.
Private SMTP is the budget play. Cheap volume, flexible, but you're relying on variable shared IPs and deliverability that can be 35–50% worse than Google. Use it as a supplement, never as your primary sending infrastructure.
The deliverability gap between inbox types is not a marginal difference. At scale, running the wrong infrastructure on a $500/month spend could mean 9,000 fewer emails landing in inbox per day compared to the right setup.
Why diversification is the professional move
Single-provider dependency is the most common infrastructure mistake we see. It creates two risks: deliverability concentration (one provider's reputation problems become yours) and operational fragility (rate limits, suspensions, or pricing changes can kill a campaign mid-flight).
The right approach is a tiered stack built around intent:
Tier 1, Google Workspace for your highest-value sequences. Decision-makers, enterprise ICPs, accounts where one reply can close a $20k+ deal. Pay the premium. It's worth it.
Tier 2, Outlook Premium for your mid-funnel, high-volume sequences. Solid deliverability at a fraction of the Google cost. Ideal when you're sending at scale to a warm, segmented list.
Tier 3, Outlook Normal or Private SMTP for broad prospecting, list-testing, and volume plays where the economics demand lower cost-per-inbox.
At Maildeck, we provision all four inbox types, with full DNS setup, warmup scheduling, and domain management handled for you. The infrastructure question becomes a configuration decision, not an operational burden. We've provisioned over 650,000 inboxes and counting.
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30% off all Maildeck plans
Build your diversified inbox stack at the best price we've offered this year. Google Workspace, Outlook Premium, and Outlook Normal, all included.
Offer expires in 5 days. Discount applied at checkout.
If you've been running a single inbox type, now is the time to fix that. Diversification isn't complexity, it's protection. And at 30% off, there's no better time to build the stack properly.
