Mailboxes for Instantly and Smartlead: Your Options Compared

You can fill Instantly or Smartlead with sending accounts in four ways: buy them inside the sequencer (Instantly done-for-you or pre-warmed accounts, Smartlead SmartSenders), buy them from a mailbox vendor and connect them, or bring mailboxes you already run. Inside the sequencer, a Google account costs $4.50 to $5 a month and a pre-warmed one $9 to $10, and the accounts can't leave that tool. Outside mailboxes cost from $2.50 a month and connect with an API key, a CSV or SMTP/IMAP logins.

We make Outreach2day, cold email infrastructure: SMTP/IMAP mailboxes at $2.50 each a month with warm-up and a sending engine included. For the sequencer plans themselves, see Instantly pricing and Smartlead pricing.

The Options Side by Side

We make Outreach2day, so it is listed first; the other rows use each vendor's own public pages, checked September 2026.

Sources for every row are listed at the end. Instantly's plans overview says: "Without the Email Outreach plan, your DFY/Pre-warmed accounts will be paused automatically after the trial period." Instantly's done-for-you help article says the accounts "are exclusively configured for use within the Instantly platform," and Smartlead's SmartSenders FAQ says "domains and mailboxes bought through SmartSenders can't be transferred and used outside of Smartlead." SmartSenders domains also run "on a fixed 12-month term from the date of purchase — there is no renewal."

What the Choice Changes

Portability. Accounts bought inside a sequencer stay in that sequencer. If you move from Instantly to Smartlead, or run both, the accounts and domains don't come with you. Mailboxes from an outside vendor connect to any tool that accepts SMTP/IMAP or the vendor's sync.

Price per mailbox. At 100 mailboxes, the mailbox line is $500 a month with Instantly done-for-you accounts, $450 with SmartSenders Google or Outlook, and $250 with Outreach2day. The sequencer plan is the same in each case. The full-stack totals at 25, 100 and 400 mailboxes are in our provider comparison.

Mailbox type. Instantly and Smartlead sell Google accounts; Smartlead also sells Outlook and SMTP. Outreach2day mailboxes are SMTP/IMAP on your own domains, not Google Workspace or Microsoft 365.

Warm-up. Instantly and Smartlead include warm-up in their plans for any connected account. Outreach2day includes warm-up in the $2.50: each mailbox sends 25+ warm-up emails a day to Google recipients, 25 to Outlook and 25 to other providers. When you connect our mailboxes to a sequencer, warm-up keeps running in Outreach2day.

Skip the sequencer fee. Outreach2day includes a sending engine (campaigns, sequences, one inbox for replies from all mailboxes), so you can send without an Instantly or Smartlead plan. Keep the sequencer if your team already works in it; connect the mailboxes and pay $2.50 a mailbox instead of $4.50 to $5 for a Google account bought inside the sequencer.

Connect Outreach2day Mailboxes to Instantly or Smartlead

1. Order mailboxes and domains. Buy .com ($13 a year) or .info ($5 a year) domains in the app, or connect your own by pointing the nameservers (24 to 48 hours). Plan up to 5 mailboxes per domain. New mailboxes are ready within 24 hours, with SPF, DKIM and DMARC set automatically.

2. Start warm-up and wait. Turn on warm-up for the new mailboxes and send no cold email for at least 14 days. The timeline is in how long to warm up.

3. Create an API key in the sequencer. In Instantly, create an API v2 key in your workspace; Instantly's API is available on every plan. In Smartlead, generate the key in your dashboard settings; Smartlead's API starts at the Pro plan, so the Base plan can't use this connection.

4. Connect the sequencer in Outreach2day. Open the Sequencers page in the app, choose Instantly or Smartlead and paste the API key.

5. Check the accounts in the sequencer. The mailboxes are added to that Instantly or Smartlead account. With auto-export and auto-reconnect turned on for the connection, mailboxes you create later are added too, and mailboxes that drop out of the sequencer are reconnected.

6. Set sending limits. From day 14, set a low daily limit per mailbox in the sequencer and raise it to up to 25 cold emails per mailbox per day by around day 21. See cold emails per mailbox per day.

To do the same from code, the REST API has endpoints to connect a sequencer, export mailboxes and reconnect them; see add email accounts to Instantly or Smartlead via API.

Other ways to connect

• CSV. Export mailboxes as a CSV in the import format of the tool you use. Instantly and Smartlead have their own templates, and so do 12 other tools, including Reply.io, Apollo, Snov.io, Saleshandy and EmailBison.

• SMTP/IMAP by hand. Every CSV carries each mailbox's SMTP and IMAP logins. Any tool that accepts SMTP/IMAP accounts can use them; add them one at a time in the tool's account settings.

Which Option Fits

• You need to send this week: pre-warmed accounts from Instantly or SmartSenders, at roughly twice the price of a fresh account and locked to that tool. See pre-warmed inboxes for what "pre-warmed" means on each vendor's page.

• You use one sequencer and never plan to leave: the sequencer's own accounts save a setup step. Compare the monthly mailbox price over a year before deciding.

• You run more than one sequencer, or several clients: outside mailboxes that connect to any tool. At Outreach2day, each client gets its own free workspace with its own domains and mailboxes.

• You want to drop the sequencer bill: mailboxes with a sending engine included.

To size the order, divide your daily cold volume by 25 for mailboxes and the mailboxes by 5 for domains. For what a whole setup costs at 1,000 to 20,000 emails a day, see how much cold email costs.

FAQ

Can I use my own mailboxes in Instantly?

Yes. Every Instantly plan allows unlimited email accounts, your own or bought from Instantly. Accounts you bring can also be used in other tools; Instantly's done-for-you accounts can't.

What are Instantly DFY accounts?

Google accounts that Instantly sets up for you on domains it buys: $5 per account a month and $15 per domain a year, up to 5 accounts per domain. Instantly keeps the domains, and the accounts work only inside Instantly.

How much are Smartlead SmartSenders mailboxes?

$4.50 a month for a Google or Outlook mailbox with a $13 domain, $3.99 for Mailreef SMTP with a $19 domain and a 75-mailbox minimum, and $9 for a pre-warmed mailbox with an $18 domain.

Can I move Instantly or Smartlead mailboxes to another tool?

No. Both vendors say their accounts can't be used outside their platform, and Instantly says it can't transfer its domains to you.

Do I still need warm-up in the sequencer if the mailboxes are warmed elsewhere?

Warm-up for Outreach2day mailboxes is included in the $2.50 and runs in Outreach2day, whichever sequencer you connect them to. Keep it running while you send. See keep warm-up running while sending.

Sources

Checked September 2026:

• Instantly plans overview: $5 done-for-you Google, $10 pre-warmed, $4 AirMail, $15 domain; accounts paused without an Outreach plan; accounts cancelled in Email Accounts & Domains.

• Instantly done-for-you help: up to 5 accounts per domain, Instantly keeps domain ownership, use only within Instantly, cancellation takes effect immediately.

• Instantly pre-warmed accounts: batches of 5, cancellation takes effect immediately and mailbox access ends.

• Instantly pricing.md: unlimited email accounts, warm-up and API access on every plan.

• Instantly API: API v2 key created in the workspace.

• SmartSenders pricing: $4.50 and $13, $3.99 and $19 with a 75-mailbox minimum, $9 pre-warmed and $18, 1 to 20 domains per Zapmail order.

• SmartSenders FAQ: no transfer or use outside Smartlead, fixed 12-month domain term, full-month charge on mid-month deletion.

• Smartlead pricing.md: "Pro and above. Base does not include API and webhooks."

• Smartlead API: API key generated in dashboard settings.

• Zapmail: plans, $13 .com, domains bought through Zapmail are yours, warm-up handled, monthly with no long-term contract, no refunds.

• Premium Inboxes: per-inbox tiers, warm-up started in your sequencer.

• Premium Inboxes refund policy: no refunds once a license is activated.

• Maildoso pricing: $2.50 per mailbox on the 30-mailbox plan ($75), $12 domains ($15 from October 1, 2026) registered with Maildoso while in use, warm-up not included.

Order mailboxes, connect your sequencer by API key, and start warm-up the same day.

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