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Maildoso

Inbox infra

SMTP-first cold infra with self-healing mailboxes, IP rotation, and API or MCP. Optional Google Workspace SKUs.

The verdict

Maildoso has the highest Reddit testing volume in this category for 2025 and 2026. It is strong when you optimize COGS and accept SMTP tradeoffs, but you should monitor placement weekly.

Skip it if your team refuses anything but official Google or Microsoft tenants.

What operators say

“~10% ... Multiple mailboxes → Using Zapmail, Inboxkit, Maildoso for infra → Using Instantly.ai, Smartlead to send emails…”

Best for

Volume operators optimizing COGS, API or MCP provisioners, and teams feeding mailboxes into a sequencer.

Not for

Teams that refuse anything but official Google Workspace or Microsoft tenants only.

Pricing truth

SMTP starts at $75 per month for 30 mailboxes ($2.50 each) and drops to $0.49 per mailbox at 1,000. Checked 13 Sep 2026. Google Workspace SKU dollar amount is a Gap this pass.

When we use it

  • Scale SMTP fleets where dollars per mailbox and self-healing IP rotation dominate total cost.
  • Provision through API or MCP into sequencers without dashboard click-ops.
  • Diversify official Google Workspace with cheap SMTP for spray or top-of-funnel volume.
  • Skip when policy demands only native Google or Microsoft Admin tenants.

How to wire it

  1. Buy an SMTP tier, register or bring domains, and let API or MCP create mailboxes plus SPF, DKIM, and DMARC.
  2. Export credentials into your sequencer and cap cold sends at 15 or fewer per day per mailbox.
  3. Mix Google Workspace SKUs if available, and keep SMTP for cheap top-of-funnel volume only.
  4. A/B about 50 SMTP mailboxes against DIY API or done-for-you peers on the same list and copy before cutover.

Margin notes

  • Expect SMTP placement drift around weeks 7 and 8. Use Slack support for IP moves when it shows up.
  • Prefer 8 or fewer mailboxes per domain, and keep targets B2B. Free-mail ESPs are weaker here.
  • Monthly plans do not include domains. Budget about $12 per year each.
  • Reply-rate A/Bs versus DIY API peers often roughly tie. List and copy still win.
  • Custom counts live under Packages and Add-ons. Go AE path above 10k mailboxes.