The best Azure mailbox provider for most cold email teams in 2026 is Frostmailer. A €30 tenant includes the .com domain, DNS, warm-up and 24/7 support, with 25, 50 or 100 inboxes for the same price. It also offers pre-warmed tenants, a REST API and MCP server, and a done-for-you option if you would rather not build anything yourself.
Below are seven Azure and Microsoft mailbox providers compared on price, what the price includes, setup time, sending guidance and support. Every competitor figure comes from that provider's own website, checked on 9 November 2026. Frostmailer prices are in euros, the others in US dollars.
Quick Comparison
| Provider | Price | Inboxes | Domain included | Setup | Support |
|---|---|---|---|---|---|
| 1. Frostmailer | €30 per tenant a month; pre-warmed €50 | 25, 50 or 100 per tenant | Yes, one .com per tenant | About 24 hours | 24/7 |
| 2. InboxKit | $30 per tenant a month; pre-warmed $30 to $50 | Up to 100 per tenant | Not listed for standard Azure | Not stated on pricing page | Email and chat |
| 3. WarmInboxes | $50 per domain a month; pre-warmed tenant $69 a month | 25 to 100 per tenant | No, .com domains $12 | 48 to 72 hours | 24/7 WhatsApp |
| 4. Hypertide | $25 per domain a month | 25 per domain | Bring your own or order through Hypertide | 4 to 6 hours | Not stated |
| 5. ScaledMail | $50 per domain a month | 25 per domain | Registration or connection included | 24 to 72 hours | Dedicated Slack channel |
| 6. Icemail | $30 per domain a month | 100 per domain | Not stated | "In minutes" | Chat |
| 7. Cheap Inboxes | $20 first month, then $18 a month | Up to 20 per domain | Yes | 10 minutes to 24 hours | 24/7 |
The headline price is only part of the cost. Check what you pay for the domain, DNS, warm-up and support on top of the tenant, and how many inboxes each provider puts on one domain.
What to Compare Before You Buy
- Billing unit. Some providers charge per tenant, some per domain. A $25 domain with 25 inboxes costs more per inbox than a €30 tenant with 100.
- What is included. Domain, DNS records (SPF, DKIM, DMARC), warm-up and support are extras with several providers.
- Sending guidance. Mailbox count is not sending capacity. Ask how many emails per inbox or per domain the provider recommends.
- Connection to your sender. Confirm the provider connects to the sequencer you use, and whether it uses OAuth or SMTP app passwords.
- Support when something breaks. A blocked tenant at 2 AM costs a day of sending if nobody answers.
1. Frostmailer: Best Overall Azure Provider
Frostmailer gives you the most included in one price. One tenant costs €30 a month and comes with a .com domain, SPF, DKIM and DMARC configured, warm-up and 24/7 support. You pick 25, 50 or 100 inboxes per tenant at the same price, so 100 inboxes works out at €0.30 each. Frostmailer recommends 50 per tenant.
Pricing
- Azure tenant: €30 a month, minimum one tenant.
- Pre-warmed Azure tenant: €50 a month, with four weeks of warm-up done before delivery. Minimum two tenants.
- Domain masking (Stealth Redirect): about €1 per domain a month.
- Done-for-you Build and Release: from €1,000 a month for 500 accounts on 10 domains, with copy, campaign setup in Smartlead and the first month of leads included.
Setup and sending
Tenants are live in about 24 hours. Each tenant sends about 200 emails a day in total, which is about 4 per inbox at the recommended 50 inboxes. Keeping volume at that level protects the tenant's reputation, and you scale by adding tenants rather than pushing each inbox harder. For larger fleets, Frostmailer also runs managed infrastructure rotation, replacing domains on a schedule so sending capacity does not decay.
Integrations and automation
Mailboxes connect to EmailBison, Smartlead, Instantly, PlusVibe, Success.ai and MasterInbox. You can order in the app, through the REST API, or through the MCP server, which lets an AI agent place and manage orders.
Best for: agencies and in-house teams that want the domain, DNS, warm-up and support in one price, with room to scale to hundreds of tenants.
2. InboxKit
InboxKit charges $30 per Azure tenant a month for up to 100 mailboxes, the same headline structure as Frostmailer. Pre-warmed Azure tenants are priced by warm-up age: $30 for domains warmed 2 to 4 weeks, $40 for 4 to 8 weeks and $50 for 8+ weeks, plus a one-time domain fee from $12.50 per pre-warmed domain.
The pricing page does not list a domain price for standard Azure tenants or state setup time or sending limits. Warm-up is sold as a per-mailbox add-on. Support is email and chat, with dedicated support for very large deployments.
Compared with Frostmailer: similar tenant price, but no domain listed in the standard tenant price and no published 24/7 support.
3. WarmInboxes
WarmInboxes focuses on pre-warmed inboxes. Its pre-warmed Azure tenant holds 100 inboxes and costs $69 a month on monthly billing, $60 on two-month billing and $50 on quarterly billing. Fresh Azure tenants with 25 to 100 inboxes cost $50 per domain a month, monthly billing only.
Fresh plans do not include a domain; .com domains are $12. Delivery is 48 to 72 hours after payment. Support is 24/7 over WhatsApp, and integrations include Instantly, Smartlead and EmailBison.
Compared with Frostmailer: Frostmailer's pre-warmed tenant is €50 a month on monthly billing with the domain included, and its fresh tenant is €30 with the domain, against $50 plus a domain here.
4. Hypertide
Hypertide's Entra (Microsoft) offer is $25 per domain a month with 25 inboxes per domain, minimum one domain. Its page states up to 3,000 sends per domain a month, based on business-day sending. Setup is typically 4 to 6 hours, warm-up is enabled as part of deployment, and you bring your own domain or order one through Hypertide.
Compared with Frostmailer: 100 inboxes on Hypertide means four domains at $100 a month. On Frostmailer, the same 100 inboxes cost €60 on two tenants at the recommended density, or €30 on one.
5. ScaledMail
ScaledMail's Outlook package costs $50 per domain a month for 25 mailboxes, with up to 10 emails per mailbox a day. Domain registration or connection is included in every package. Setup takes 24 to 72 hours, support runs through a dedicated Slack channel, and reporting is a $5 per domain add-on.
Compared with Frostmailer: 100 inboxes on ScaledMail is four domains at $200 a month, against €30 to €60 on Frostmailer.
6. Icemail
Icemail's Azure offer is $30 per domain a month for 100 mailboxes on a single domain, with 5 emails per mailbox a day (500 a day per domain). Mailboxes connect through SMTP/IMAP credentials and app passwords, and export to Instantly, Smartlead, EmailBison and other sequencers. DNS is set up so the mailboxes are ready for your own warm-up, which you run over about 14 days. The page does not say whether the domain is included.
Compared with Frostmailer: similar price per 100 inboxes, but warm-up is yours to run and the connection is SMTP app passwords rather than Microsoft OAuth.
7. Cheap Inboxes
Cheap Inboxes lists up to 20 "Microsoft-powered" inboxes on a single domain, domain included, for $20 the first month and $18 a month after. It does not describe the offer as an Azure tenant. Its FAQ says setup takes 10 minutes, while its comparison table says within 24 hours. Support is advertised as 24/7, and inboxes export to Instantly, Smartlead and other sequencers. No sending limits are published.
Compared with Frostmailer: fewer inboxes per domain, so 100 inboxes means five domains, and no published sending guidance.
What 100 Azure Inboxes Cost a Month
| Provider | Setup for 100 inboxes | Monthly cost | Domains included |
|---|---|---|---|
| Frostmailer | 2 tenants x 50 (recommended) or 1 tenant x 100 | €60 or €30 | Yes |
| InboxKit | 1 tenant | $30 | Not listed |
| Icemail | 1 domain | $30 | Not stated |
| WarmInboxes | 1 tenant | $50 plus a $12 domain | No |
| Cheap Inboxes | 5 domains x 20 | About $90 at the listed rate | Yes |
| Hypertide | 4 domains x 25 | $100 | Bring your own or order |
| ScaledMail | 4 domains x 25 | $200 | Yes |
Add your sequencer subscription to every option. Prices exclude VAT and sales tax.
Which Provider Fits Your Team?
| You want | Best pick |
|---|---|
| Domain, DNS, warm-up and support in one price | Frostmailer |
| Pre-warmed tenants on monthly billing | Frostmailer (€50, domain included) |
| 24/7 support | Frostmailer |
| Ordering through an API or AI agent | Frostmailer (REST API and MCP server) |
| Someone else to build the whole outbound system | Frostmailer Build and Release |
| Low inbox count per domain | Hypertide or ScaledMail (25 per domain) |
| A small test on a single domain | Cheap Inboxes |
No provider can guarantee inbox placement. Results still depend on your list, copy, sending volume and how you warm and rotate your domains.
FAQs
What is an Azure mailbox for cold email?
An Azure mailbox is an Outlook inbox hosted in a Microsoft tenant set up specifically for outbound. Because a tenant can hold many inboxes on one domain, the cost per inbox is far lower than buying Microsoft 365 seats one by one.
How many emails can an Azure inbox send a day?
It depends on the provider's guidance and how many inboxes share the tenant. Frostmailer tenants send about 200 emails a day in total, which is about 4 per inbox at 50 inboxes or 2 to 3 per inbox at 100. Scale by adding tenants rather than pushing each inbox harder.
How many tenants do I need?
Divide your target daily volume by about 200. To send 4,000 emails a day, you need about 20 tenants, which is 1,000 inboxes at 50 per tenant. The mailbox calculator works it out for you.
Should I buy pre-warmed Azure tenants?
Buy pre-warmed if you need to send at full volume on day one. Frostmailer's pre-warmed tenants arrive with four weeks of warm-up done, for €50 a month each with a two-tenant minimum. If you can wait, standard tenants at €30 include warm-up too.