Cheapest Way to Warm Up 50+ Inboxes: Real Monthly Costs

The cheapest way to warm up 50 or more inboxes is a plan that does not charge per inbox. If you already pay for an outreach platform with unlimited warm-up, use it. If you only need warm-up, BobWork Email Warm-up costs $120 a month for 50 inboxes and $180 for 100, against $750 to $1,450 on the common per-inbox tools. Pick wrong and the warm-up bill outgrows the campaigns it protects.

This page works out the totals for 50, 100 and 200 inboxes across the pricing models that exist, and is honest about where we are not the cheapest. If you are setting up the agency workflow itself (naming, client separation, reporting), read email warm-up for agencies alongside it.

What decides the cost at 50+ inboxes?

At five inboxes, every warm-up tool looks affordable. At fifty, the billing unit matters more than the headline price. There are three models.

Per inbox. You pay a fixed amount for every mailbox you warm. Warmup Inbox, Lemwarm, MailReach and Folderly work this way. The cost grows in a straight line, so 100 inboxes cost ten times what 10 do.

Flat fee for unlimited accounts. Some outreach platforms bundle warm-up and say it covers unlimited email accounts. Instantly Growth, Smartlead Base and TrulyInbox Starter are priced this way. The warm-up cost stops growing with inbox count. You are, however, buying a sending platform or a plan with its own limits.

Free tier plus steps. BobWork Email Warm-up is free for the first 10 mailboxes per account. Each active mailbox above 10 is billed monthly, and the price per mailbox drops as the account grows:

Every extra mailbox is billed at the step the account has reached, not band by band. So once you have 50 extra mailboxes, all of them cost $2. An account can hold up to 200 mailboxes. Paused mailboxes are not billed, and billing is prorated through Stripe. Full details are on the pricing page.

How much does BobWork cost for 50, 100 or 200?

These totals come straight from the billing function the app uses. They are monthly figures for active mailboxes.

How do competitors price 50+ inboxes?

Prices below were read from each vendor's pricing page at the time of writing: Warmup Inbox, Lemwarm, MailReach, Mailwarm and Instantly on 3 October 2026, TrulyInbox, Smartlead and Folderly on 4 October 2026, and Woodpecker on 17 October 2026. Check before you buy, because prices change.

Mailwarm's Scale plan is $479 for 10 mailboxes. Pricing beyond 10 is not stated on their pricing page, so it is left out of the totals.

The honest reading: at 50 or more inboxes, flat-fee plans from Smartlead, Instantly and TrulyInbox cost less than we do. If you already send campaigns through Smartlead or Instantly, their bundled warm-up is effectively free to you, and adding a second tool may not be worth it.

When is a standalone tool still the better buy?

Flat-fee plans are cheapest on paper, but the price is only one line of the decision. A standalone warm-up tool makes sense in these cases.

You do not use their sending platform. Instantly and Smartlead price warm-up as part of an outreach product. If you send from your own tool, a CRM, or BobWork Outbound, you would pay for a platform you do not use.

You want the first 10 free with no clock. Among standalone warm-up tools, only TrulyInbox (1 account, 10 emails a day) and BobWork Email Warm-up (up to 10 mailboxes, 3 to 30 emails a day each) offer a free-forever plan. Every other tool listed above is a trial or paid. For a small agency, 10 free mailboxes may cover every client.

Some clients need isolation. The competitors above run vendor-operated or customer networks, and none lists a per-account private pool on the pages we read. BobWork uses a shared warm-up network by default, and any account can switch to a private pool (Mailbox pool → Pool mode). Then only that account's mailboxes write to each other, and nobody outside the account receives their addresses. A private pool needs at least two mailboxes.

Your inboxes are on Zoho, Lark or a hosting provider. Instantly lists Google Workspace and Microsoft Outlook. BobWork connects Gmail and Google Workspace, Zoho Mail (including the free Zoho plan via its API), Lark Mail, Yahoo, iCloud, Amazon SES, SendGrid, Mailgun and any IMAP plus SMTP mailbox.

Many of your inboxes are Microsoft 365. Then choose a tool that lists Outlook support. BobWork does not support Outlook or Microsoft 365 yet, because Microsoft requires OAuth for that connection. Every competitor in the table lists Outlook, except Folderly, where it is not stated.

What does sending add to the bill?

Warm-up is only half the cost if you also need a tool to send the campaigns. Flat-fee platforms such as Instantly and Smartlead include sending in the plan, within limits we did not compare. A standalone warm-up tool does not, so add your sending cost before comparing.

BobWork's optional Outbound feature sends sequences from your own warmed mailboxes for $2 per 1,000 emails, with no monthly fee. Only mailboxes that passed the ready check can send, at up to 30 cold emails a day each in their first week after ready and 50 a day after that.

A worked example, stating the assumptions: 50 mailboxes, 30 cold emails a day each, 22 working days a month. That is 33,000 emails, or $66 in Outbound credits, on top of $120 for warm-up. Total: $186 a month. At 100 mailboxes with the same pattern it is 66,000 emails ($132) plus $180 for warm-up, or $312.

Those totals are higher than a $39 or $47 flat plan. They are lower than any per-inbox warm-up tool before you even add a sending tool.

One more limit to plan for: a BobWork account holds up to 200 mailboxes. Beyond that, you need a second account or a different tool.

How do you run warm-up for 50+ inboxes without manual work?

At this scale, connecting mailboxes one by one in a dashboard gets slow. Plan the operations as carefully as the price.

Connect in bulk through the API

BobWork's REST API is free. It uses personal keys (bwk_…, up to 5 per account) with Bearer auth and allows 120 requests per minute per key. Its 44 endpoints cover mailboxes, warm-up stats, SPF, DKIM and DMARC checks, and connecting IMAP or Zoho mailboxes. A short script can connect a client's 40 mailboxes from a CSV in one go. Docs are at /api.

Let an AI assistant do the checks

The same key works with a remote MCP server at https://app-emailwarmup.bobwork.ai/mcp, with 39 tools. Claude, ChatGPT, Cursor and other MCP clients can list mailboxes, read health scores, check DNS for a client domain and report which inboxes passed the ready check. Our MCP server guide walks through the setup.

Report one number per mailbox

Every mailbox gets a health score from 0 to 100 (Healthy 85 or above, Watch 60 to 84, At risk below 60, Blocked when login or permission failed). The 7-day spam rate is the share of that mailbox's warm-up mail that recipients found in Spam. A mailbox is ready for outbound after 7 days of warming, a spam rate at or under 10%, and at least 30 warm-up emails received. Those three numbers are what a client wants to see.

Keep each inbox inside safe limits

Adding inboxes is how you scale volume, not pushing each one harder. Warm-up ramps from 3 to 30 emails a day per mailbox, adding 2 a day. During campaigns, keep warm-up at 10 to 15 a day and real outreach at 30 to 50 per mailbox. Pause any mailbox whose spam rate rises above 5% for a few days. The how many cold emails per day guide does the inbox-count arithmetic.

Do this now

If an outreach platform you already pay for covers warm-up for unlimited accounts, keep using it. If it does not, or you want 10 mailboxes free with no time limit and an optional private pool, BobWork Email Warm-up is free to start with no card. The free email warm-up tools comparison covers the other free options.

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