Microsoft 365 Mailboxes for Cold Outbound

Mailionaire doesn't send the mails - we provide the sender accounts (= infrastructure). You send the mails by yourself with a sequencer.

For everyone doing cold outbound: teams that win new customers with cold emails and use Instantly, Smartlead or any other sequencer. Mailionaire provides the sender accounts for that.

• Only $0.25 per inbox. No setup fees, no other costs.
• Tenant quality: we use our own tenants. We don't buy them from resellers and we don't use pooled ones. We manage the tenants directly and hold the provider contracts through our own Swiss company - not some made-up LLC that pools 1000s of orders. We don't need 10 employees and don't have to scale to be profitable, so we can do that. Otherwise it's hard to scale with that quality approach.
• Other providers don't optimize for deliverability and longevity, because it's not their core business or they lack the technical expertise. Eg they don't have proper Microsoft Entra permissions or backend automations. Mailionaire has a single focus on Microsoft.
• Mailboxes are created within 1-4 hours. 100% automated. Others have overseas VAs doing that manually over a few days.
• 100% automated end-to-end setup. You buy the mailboxes and Mailionaire adds them to your sequencer (EmailBison, Instantly, PlusVibe and Smartlead) and switches on warmup. No CSV, no connecting 100s of inboxes.
• The most advanced API and the best UI: 70 API endpoints, others have 10s. Mailionaire is built from the ground up.
• Support directly with the developer/founder. If you have a problem or a feature request, it's usually done within 12-48 hours.

I'm the founder and developer of Mailionaire (Robin Kunz). I have been doing cold outbound for the last 10 years. Mailionaire has been the internal tooling of my own agency for more than a year. So Mailionaire is built and used by cold emailers like you.

Mailionaire is new in the market. Hence the intro pricing.

$25 per order per month. 1 order = 1 domain and you bring that domain yourself. In that order you choose anywhere from 1 to 100 mailboxes. The total stays $25.

So the cost per mailbox depends on how many you use:

• 100 mailboxes: $0.25 each per month
• 50 mailboxes: $0.50 each per month
• 1 mailbox: $25 per month

I use 100 per tenant myself, as do most customers, but you can choose fewer. The fewer mailboxes per domain, the "safer". Eg for 1,000 mailboxes you place 10 orders with 100 each ($250/month) or 20 orders with 50 each ($500/month).

No setup fees and no other fees. Your domains and your sequencer you bring yourself - they're not provided by us, so their costs are separate.

Good tech and one person doing it all (developer/founder), not a bloated company with countless employees such as devs or sales.

On top, this is an introductory price for early users. Mailionaire will always be cheaper than the competition.

It's a monthly subscription: $25 per domain/order, including up to 100 sender accounts. When you add a domain, you pay a prorated amount for the rest of that month. Eg if you add a domain halfway through October, you only pay for the rest of October.

After that, all your active domains are billed together on the 1st of each month, with one consolidated invoice. Additional purchases generate a separate prorated charge at the time of purchase.

Yes, per order. The introductory rate stays locked for each order as long as that order is active. It isn't an account-wide guarantee: new orders placed after a price increase use the pricing in effect at that time.

Minimum is 1 order ($25 per month). No commitment.

No, we don't do free trials. For testing the API there's a sandbox with test API keys, simulated orders and webhooks. It doesn't create real Microsoft mailboxes or send email.

You cancel a domain in the app or through the API. The cancellation takes effect at the end of the paid term, not immediately - we pass on Microsoft's cancellation terms. There are no refunds.

Exchange Online shared mailboxes, like every other Microsoft infra provider uses. They're not shared with other customers.

Each tenant runs on a paid Microsoft 365 Business Basic subscription. No trial subscriptions.

Yes. Each domain gets its own dedicated Microsoft 365 tenant. Customers never share a tenant, so every tenant is 100% isolated.

It depends. A few days or weeks.

No. We manage the tenant administration, so tenant admin access isn't included. Sequencers connect via OAuth.

If you need your own integration, Mailionaire also supports customer-owned Microsoft Graph apps. That requires verification and activation on our side.

No. Mailionaire's focus is Microsoft only - and doing that as the best in the market.

No. The 2028 retirement applies to Azure Communication Services, including ACS Email - not to Microsoft 365 tenants or Exchange Online mailboxes. Mailionaire uses Exchange Online, so that announcement does not affect Mailionaire.

Yes, 100% automatic. We take care of SPF, DKIM and DMARC. We also enable and verify DKIM signing in Microsoft 365, regularly check the email DNS records and automatically repair missing or incorrect ones.

1-100 mailboxes per domain. I do 100, some do 25 or 50. The lower, the safer. 100 per domain is ok if you don't stress them. Otherwise go with 50 per domain.

Max 3 cold emails per mailbox per day. Microsoft is different from SMTP: more volume per mailbox burns the reputation faster.

The older a domain/sender account gets, the better (much better actually). That's why I keep the volume low and grow the lifespan of the sender accounts.

Warmup comes on top: 5 warmup emails per mailbox per day.

With Microsoft you send much less per mailbox and spread the volume across more accounts. So you can't replace 60 Gmail inboxes with 60 Microsoft inboxes and expect the same daily volume.

Eg 10,000 sends per day, planned on the safe side with 3 cold emails per mailbox and 25 mailboxes per domain: 3,350 mailboxes on 134 domains, $3,350/month. With 100 mailboxes per domain, it's 34 domains, $850/month. On top, I recommend backups.

Warmup runs in your own sequencer. Mailionaire creates the mailboxes within 1-4 hours, adds them to your sequencer and switches on warmup there, with 5 warmup emails per mailbox per day. It's all automatic.

After 14 days of warmup, the mailboxes are ready for cold email.

At least 14 days. The longer the warmup, the better. If it's urgent you can go with 1 week, but you'll likely burn the mailboxes and it's not worth the hassle. I usually do 2-8 weeks.

My placement tests with EmailGuard always show 100%. I also send for Swiss and European enterprises with SOC2 etc. and my mails land in primary.

It depends on your offer and your skills. I had campaigns with 40% reply rates and some with 0.5%. Both were perfect for their use case.

Depends. It's all seasonal and in the end it's a numbers game. Google Workspace costs like $2.50-$3.50 per sender account. So it's hard to beat Microsoft sender accounts - Google would need to be 10x better.

Yes. The mailboxes can send to recipients at any email provider, not just Outlook and Google. Inbox placement depends on several factors, including sender reputation, authentication, email content and sending volume.

Your domains remain yours. There are no refunds or replacements. If a sender account doesn't perform well, order new ones.

That's why I recommend backups. Eg I keep a 100% backup ratio: for 1,000 sender accounts, I have 1,000 more warming up in the background. I swap them in for a new client, for volume spikes or - the main reason - when sender accounts or domains get flagged.

Yes. I monitor each client's performance. If someone blasts through my tenants recklessly and doesn't follow basic best practices, I close their account. If best practices are followed, there is no problem.

No. Mailionaire is a product for people who are experienced with cold emails and know the basics.

Fully. You connect your registrar and your sequencer once. After that you have your full system:

• Branded domains are assigned to the right workspace automatically. Unbranded domains are no problem either.
• Adding domains and provisioning them takes a few clicks.
• Usernames: generated automatically (you pick the region mix and gender balance), your own names with custom formats or a CSV upload.
• At the end, the mailboxes land in your sequencer. Fully automatic.

So you can customize a lot - or just let it run.

Yes, you bring your own domains. Supported registrars, fully automatic end to end: Porkbun, Namecheap, Spaceship and Dynadot. If you use another one, let us know and we'll check if we can integrate it.

We limit domains to .com and a few other tier-1 domains, because cheap $1 domains hurt deliverability. Domains already attached to another Microsoft tenant must be cleanly detached first.

Yes, 100%. Your own domains and your own naming, eg john@getyourcompany.com.

EmailBison, Instantly, PlusVibe and Smartlead. Mailionaire adds the mailboxes to your sequencer automatically - no CSV, no connecting 100s of inboxes. If an integration is missing, tell us and we'll add it.

Yes. You keep your sequencer and your existing Gmail or other accounts. The Mailionaire mailboxes are added alongside them.

In general I'd always diversify and have backups. Start with a few orders, get familiar with Microsoft and then scale rapidly.

Mailionaire handles:

• Creating and managing your Microsoft 365 sender accounts
• The technical setup, including DNS
• Connecting the mailboxes to your sequencer and switching on warmup

You handle:

• Buying the domains
• Your sequencer, eg Instantly or Smartlead. That subscription is separate.
• Your lead lists, email copy, campaigns, replies etc.

So we take care of the mailbox infrastructure and your team runs the outreach.

Yes. Mailionaire supports domain forwarding (simple or with a CAPTCHA) and domain masking. Check for yourself: gomailionaire.com

Yes. Mailionaire has 70 API endpoints, other infra providers offer 10s. Missing endpoints we build ourselves, with no overhead.

API referenceOpenAPI schemallms.txt

Yes. One Mailionaire account can manage many domains and assign them to separate workspaces.

Provisioning keys and billing stay account-wide, so there's no separate API access per end client. Attribution and rebilling to your clients happen on your side.

Email is best, but we're flexible. You write directly with the developer/founder, so problems and feature requests usually get done within 12-48 hours.

1. Request access at the top of this page. Mailionaire is invite-only right now.
2. Complete the onboarding: connect your registrar and your sequencer with their API keys. Takes 2-3 minutes.
3. Create an order and click "buy sender accounts". The mailboxes are created within 1-4 hours, added to your sequencer and warmed up there. After 14 days you're ready to send.