Short answer: Premium Inboxes has an excellent review record, simple per-inbox pricing and unlimited replacements. Frostmailer prices Microsoft per tenant rather than per inbox, includes the domain, sells pre-warmed inboxes, and its done-for-you build starts at €1,000 a month.
Side by side
| Frostmailer | Premium Inboxes | |
|---|---|---|
| Microsoft / Azure | Yes. €30 per tenant: one .com domain plus 25, 50 or 100 inboxes | Microsoft 365 Business inboxes, one price list shared with Google Workspace. No Azure tenant option listed |
| Google Workspace | Full admin, €3.00 / €2.80 / €2.50 per inbox by volume | $3.50, $3.00 or $2.80 per inbox by volume, with unlimited replacement inboxes |
| Domain included | Yes, a .com with every Azure tenant and with pre-warmed Google. For standard Google Workspace you bring your own | No. Bring your own domains (their managed ECC tier sources domains for you) |
| Pre-warmed | Azure €50 per tenant, Google €8 per inbox, 4 weeks of warm-up done | Not offered as a separate product |
| Done-for-you build | Yes. Build and Release from €1,000 a month: infrastructure, copy, campaign and first month of leads | Managed operations (ECC) at $7,500 a month, by application |
| API and MCP | REST API and MCP server on every account | API page on the site. No MCP server mentioned |
| Delivery | 10 to 24 hours | Listed as under 6 hours |
| SMTP | No | No |
Premium Inboxes details checked on 10 October 2026 from their public pages (sources below). Prices change, so confirm on their site before you buy.
When Premium Inboxes is the better choice
- You want a provider with a very large review record. Premium Inboxes shows 5.0 from over 500 Trustpilot reviews.
- You want unlimited replacement inboxes included on every tier.
- You want Microsoft 365 mailboxes billed per seat.
When Frostmailer is the better choice
- You send at volume on Microsoft. A Frostmailer tenant is €30 a month for up to 100 inboxes, against per-inbox pricing.
- You want the domain included rather than bringing your own.
- You want pre-warmed Azure or Google that can send on day one.
- You want a done-for-you build without an application process, from €1,000 a month.
Questions
Which is cheaper for Microsoft inboxes?
Premium Inboxes prices Microsoft 365 per inbox, from $3.50 down to $2.80. Frostmailer prices Azure per tenant, €30 a month for up to 100 inboxes with a .com domain included.
Do they include domains?
For Google Workspace, both ask you to bring your own domains. Frostmailer includes a .com domain with every Azure tenant and with pre-warmed Google. Premium Inboxes asks you to bring your own on its standard tiers.
Does either sell pre-warmed inboxes?
Frostmailer sells pre-warmed Azure and Google with 4 weeks of warm-up done. Premium Inboxes does not list a separate pre-warmed product.