MailRun
Alternative & Review

MailRun builds premium email infrastructure using Microsoft Azure. They target enterprise senders who want high security and speed. They automate the entire process, from buying the domains to creating the inboxes. They put your accounts on isolated tenants. This means you do not share a server environment with other senders, which protects your reputation. They charge a premium for this security.

MailRun does not have a public profile on G2 or Trustpilot.

"mailrun.ai (you can use the code JoinStuartAtMailRun for a little discount) or slicey.ai is who I would use." — Anyone have a good source for bulk Microsoft accounts?

🟢 Azure infrastructure: Microsoft Azure IPs generally have high trust and bypass strict corporate spam filters easily.
🟢 Isolated setup: They isolate your domains so other spammers cannot ruin your reputation.
🟢 Full automation: They handle everything via API, pushing the accounts directly to your sending tool.

🔴 Very expensive: Their cheapest plan is $129 a month, making it hard for smaller teams to start.
🔴 Microsoft only: You cannot diversify your sending with Google Workspace accounts.
🔴 Strict limits: They only allow 10 inboxes per domain, forcing you to buy more domains to scale.

Maildoso is a cold outreach infrastructure provider – we offer domains, SMTP mailboxes, and Google Workspace accounts. The company was founded in August 2023 in Granite Bay, California, by Nikita Bykadarov (Nikita Maildoso).

While other providers offer shared or dedicated IPs, we have developed IP rotation. This means your emails are sent from hundreds of different IPs (making it harder for spam filters to detect a sending pattern), and whenever any IP gets blacklisted, we automatically swap it out for a clean one.

We have also implemented self-healing mailbox technology, which both restores burned-out mailboxes and protects your active email accounts.

The result? As of May 2026, the spam rate across our entire network of mailboxes is around 5%.

G2: 4.7/5 (181 reviews)

"Tried it mainly because of the good price, but ended up sticking with it since deliverability’s been pretty stable so far" – Thinking about trying "Maildoso". Has anyone here used it? Is it actually better than other tools?

"I tested a small batch first and results were comparable to our Google setup. Ended up moving more campaigns there because of the lower cost. That's a good strategy, buy small package and compare with your current setup" – I want to try Maildoso. What do you guys think about it?

🟢 Dynamic IP Rotation: We rotate your IP addresses in real-time – if an IP gets flagged or blacklisted, we instantly swap it for a clean one before your campaign takes a hit.
🟢 Self-Healing Rotation: An automated resting period for mailboxes every two weeks that clears provider flags and recovers reputation on autopilot.
🟢 API & MCP Automation: Create domains and mailboxes, export to your sequencer in one call – or manage it all from your AI assistant through our MCP server.

🔴 Conservative Limits: We suggest sticking to 15 emails a day per box to keep your domains healthy for the long run.
🔴 Google/SMTP Focus: We do not support Microsoft 365/Outlook/Azure environments at this time.
🔴 Lack of built-in warmup. We do not have an integrated warm-up yet, but we are currently working on it.

Do not choose a provider just because they offer the cheapest inboxes. Cheap infrastructure always costs more in the long run. When your deliverability drops, you pay for it in three ways:

1. You burn expensive leads. Good B2B data costs money. If your emails land in the spam folder, you waste those leads. You pay for contacts who never even see your pitch.
2. You destroy your domains. Once spam filters flag a domain, it is incredibly hard to fix. You usually have to throw the domain away, buy a new one, and start the warm-up process all over again.
3. You lose revenue. Every email that goes to spam is a missed meeting. In B2B sales, missing one connection can cost you thousands of dollars in closed revenue.

You have to treat cold email infrastructure as an investment. Maildoso.ai gives you the technical tools to protect your domains and keep your emails in the primary inbox. It is the only way to scale outbound sales profitably.

MailRun offers mailboxes built on Azure infrastructure. While these mailboxes are very cheap (averaging around $1), the savings are illusory rather than real:

Volume Limitations: On average, you can only send 3–5 emails per mailbox (as opposed to 30 emails on Google Workspace accounts). This means you’ll need 6 times as many mailboxes, making the real price 6 times higher.

Reliability Issues: We receive reports almost weekly that yet another Azure-based provider has been blocked. From a reliability standpoint, they are much worse – even worse than SMTP (and incidentally, SMTP often delivers better results than Google Workspace).