Buy from Zapmail directly if you need more than about 10 mailboxes. Buy inside Smartlead if you need a handful and want everything in one bill. Smartlead's own pricing page lists its Google mailboxes and one of its Outlook options as "Powered by Zapmail", so the mailbox underneath is often the same. The difference is price and packaging: Smartlead charges $4.50 per mailbox a month with no plan minimum, while Zapmail's plans work out to $2.99 to $3.90 per mailbox but start at $39 a month for 10.
Prices below come from smartlead.ai/pricing and zapmail.ai, checked on October 24, 2026.
Google pre-warmed inboxes vs Azure mailboxes for cold email
Google pre-warmed inboxes are the safer default for cold email, and Azure or Microsoft 365 mailboxes only make sense when you own the tenant and need volume that Google's limits block. Neither choice fixes a bad list, and "pre-warmed" does not guarantee inbox placement.
The sending limits are the clearest difference. Google Workspace allows 2,000 messages per user per day, 1,500 on mail merge and 500 on trial accounts, with 10,000 total recipients and 3,000 external recipients per rolling 24 hours. Microsoft 365 Exchange Online allows 10,000 recipients per day at 30 messages per minute, and Microsoft's own service description says Exchange Online is not suited to bulk mailing. On paper Microsoft looks roomier. In practice both numbers sit far above what a cold mailbox should send.
Operators in both threads converge on 20 to 30 sends per mailbox per day across two or three mailboxes per domain. One runs 200 Google and 50 Microsoft mailboxes at 15 sends each, matched one to one with warmup. At four sends a day a mailbox never builds its own reputation, so you are trusting the pool instead.
That is where pre-warmed Azure gets risky. Sellers in the thread describe pre-warmed Microsoft tenants as shared infrastructure: when Microsoft flags the tenant, every mailbox inside it goes down together. The Google version carries less of that risk but the label is still just a label. Check the seller and the account history before you pay for it.
Price the two options properly. Smartlead lists Google and Outlook mailboxes pre-warmed at $9 per mailbox per month against $4.50 fresh, and $18 per domain per year against $13. You pay double for weeks you skip.
Settle two terms before you buy: which exact Microsoft product "Azure" means, since Exchange Online mailboxes and an Azure email sending service are different products, and whether you can take over the tenant. Then buy a small batch, compare placement, and move the rest only if it holds.
Per-mailbox prices
Smartlead SmartSenders
| Mailbox type | Provider behind it | Per mailbox a month | Per domain a year |
|---|---|---|---|
| Google, fresh | Zapmail | $4.50 | $13 |
| Google with admin access | Zapmail | $4.50 | $13 |
| Outlook, fresh | Zapmail | $4.50 | $13 |
| Outlook, fresh | InfraInbox | $5.00 | $16 |
| Google or Outlook, pre-warmed | Zapmail | $9.00 | $18 |
| SMTP | Mailreef | $3.99 | $19 |
| SMTP | AeroSend | $4.20 | $13 |
SmartSenders mailboxes are bought inside Smartlead and connect to your Smartlead campaigns. Smartlead's sending plans are separate: Base starts at $39 a month ($32 billed yearly), and every plan includes unlimited email accounts.
Zapmail
| Plan | Price | Mailboxes included | Extra mailboxes |
|---|---|---|---|
| Starter | $39/month | 10 | $3.50 each |
| Growth | $99/month | 30 | $3.25 each |
| Pro | $299/month | 100 | $3.00 each |
Zapmail mailboxes can be Google or Microsoft under one plan and export to Smartlead, Instantly, lemlist and 50+ other sending tools. Yearly billing is cheaper. Domains are a separate cost.
What each costs at 10, 30 and 100 mailboxes
Monthly mailbox cost on monthly billing, before domains.
| Mailboxes | Smartlead SmartSenders (Google) | Zapmail | Cheaper |
|---|---|---|---|
| 5 | $22.50 | $39 (Starter, 10 included) | Smartlead |
| 10 | $45 | $39 (Starter) | Zapmail, slightly |
| 30 | $135 | $99 (Growth) | Zapmail |
| 100 | $450 | $299 (Pro) | Zapmail, by $151 a month |
At 2 to 3 mailboxes per domain, 30 mailboxes need 10 to 15 domains. Smartlead lists those at $13 a domain a year. Our guide on how many mailboxes per domain explains the 2 to 3 limit.
What else differs
- One vendor or two. SmartSenders keeps mailboxes, sending and billing in Smartlead. Zapmail is a second account, but its mailboxes can move to another sequencer if you ever leave Smartlead.
- Pre-warmed mailboxes. Smartlead lists Zapmail-powered pre-warmed mailboxes at $9 a month, double the fresh price. Worth it only if a campaign has a fixed start date. Otherwise, see how long it takes to warm up a new email address.
- Admin access. Smartlead offers a Google option "with Admin Access" at the same price. Ask either vendor who owns the Google Workspace organization before you commit.
- Extras. Zapmail plans include deliverability test credits, aged domains for sale and bulk DNS management. Smartlead adds its own deliverability tools and placement tests as separate plans.
The ownership question
In an r/Coldemailing thread asking "Inbox kit? Zapmail? Mail forge? Smartleads directly?", the most detailed reply made one point above price: if you don't own the underlying Workspace organization, your sending history stays behind when you leave. Six months of sending reputation is worth more than a dollar per mailbox. Ask whether you can take over the Google or Microsoft tenant, and how, before buying from any reseller. Our Zapmail review covers a reviewer's complaint about exactly this.
The same reply questioned the dedicated IP the poster was paying for at 2,500 emails a week. At that volume a clean shared setup often performs about the same.
Test before you move everything
Several replies in that thread gave the same advice: keep your best-performing mailboxes where they are, buy a small batch from the new provider, and compare reply, bounce and inbox placement rates for a couple of weeks. Deliverability between providers varies by niche and changes over time, so no review can tell you how your own campaigns will do. List quality, targeting, volume and copy usually matter more than where the mailbox came from. Our Instantly vs Smartlead deliverability comparison covers the sending side.
Which to buy from
- Under 10 mailboxes, already on Smartlead: SmartSenders. No plan minimum and one bill.
- 10 or more mailboxes: Zapmail directly. Same provider, lower price per mailbox, and portable to other sequencers.
- Not on Smartlead: Zapmail, since SmartSenders only makes sense inside Smartlead.
- Need control of the tenant: confirm ownership terms in writing with either vendor, or buy Google Workspace directly.
Mailboxes are the cheapest line in a cold email budget. Bookings depend on the list, the offer and the copy that go through them. Our guide on how to increase cold email reply rate covers all three. If you want the whole system built and run, that is what KomsGro's B2B cold outbound agency does.