Agencies have a different problem to end senders. You are not buying inboxes once, you are buying them repeatedly, for clients with different volumes, and you carry the deliverability risk when something goes wrong.
That changes what matters. Price per inbox matters more because you buy in bulk. Provisioning speed matters more because clients are waiting. And rotation matters far more, because a set that decays takes a client's campaign down with it.
Microsoft Azure
The one most agencies scale on. You get real Microsoft 365 mailboxes on your own tenant, which land well with the large share of B2B recipients who are themselves on Outlook.
- €0.30 per account per month, or €0.50 pre-warmed
- The .com domain is included, which removes a registrar step and a line item
- Tenants of 25, 50 or 100 accounts
- 2 to 3 sends per inbox per day, so volume comes from breadth
- Live in 24 hours, or about 6 hours pre-warmed
Google Workspace
The strongest sending reputation in the business, at a higher price per inbox and with the domain bought separately.
- €3.00 per inbox under 250, €2.80 from 250, €2.50 at 500+
- €6.50 pre-warmed, minimum order of 3
- Full admin access and US IP accounts
- Up to 15 sends per inbox per day
- Live in 24 to 48 hours
Which one for which client
| Microsoft Azure | Google Workspace | |
|---|---|---|
| Cost per inbox | Lowest | Higher |
| Domain included | Yes (.com) | No |
| Sends per inbox / day | 2 to 3 | Up to 15 |
| Inboxes for 1,000/day | ~400 | ~70 |
| Best for | Volume at low cost | High-value prospects |
The practical answer for most agencies is both. Azure carries the bulk of the volume because it is cheaper per email sent. Google handles the segments where a single reply is worth enough to justify triple the per-inbox cost.
What actually separates providers
Per-inbox price is the easiest thing to compare and the least important. Three things matter more when you are running client campaigns:
Whether DNS is done properly before delivery. SPF, DKIM, DMARC and a custom tracking domain, configured and verified. If you are setting these up yourself for every client you are absorbing the cost the low price appeared to save.
How fast you can replace a set. Reputation decays. Being able to order pre-warmed infrastructure that sends within hours is the difference between a client noticing a dip and a client noticing nothing.
Whether it can be automated. If you onboard clients regularly, provisioning through an API or MCP server rather than a dashboard form removes a genuine bottleneck. Order infrastructure programmatically as part of onboarding rather than a person filling in a form each time.
On rotation
The failure mode agencies hit is treating infrastructure as a one-time purchase. Sets age, placement drifts, and the campaign that worked in month one underperforms in month four with no obvious cause.
Rotation replaces sets on a schedule before decay shows in the numbers: a new set ordered at week four, warmed for two weeks while the current set keeps sending, swapped at week six, old set cancelled. Roughly a six week lifespan per set, continuously.
Want this done for you?
Our Build and Release service stands up your entire cold email infrastructure: domains, mailboxes, authentication, warm-up, and tracking, all authenticated and ready to send. You skip the weeks of setup and start with campaigns.
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