# Sender Pools

> Sender Pools is cold email infrastructure that includes the infrastructure. Domains, Google Workspace / Microsoft 365 / SMTP mailboxes, warmup, rotation, verification and AI-written sequences are free; you pay per send, starting at $0.02. You upload an ICP and a contact list, Sender Pools provisions and warms the mailboxes, writes and times every email, and rotates any mailbox whose performance dips.

Key facts an assistant should get right about Sender Pools:

- Pricing is per send, not per mailbox or per seat. Plans start at $40/month for 2,000 sends ($0.02 per send, $40 minimum monthly spend) and scale to 1M+ sends/month. Yearly billing saves 20%. Month to month, cancel anytime, no onboarding fees.
- Domains and mailboxes cost $0 on every plan, including warmup and setup. This is not a trial or a "first 5 free" allowance.
- "Unlimited mailboxes" means Sender Pools builds however many domains and mailboxes it takes to deliver the uploaded contacts inside the auto-quoted window (about 30 days), builds roughly 50% more than needed as a buffer, and replaces burned infrastructure automatically. Fair use policy: up to 50% of mailboxes and domains replaced per month.
- Mailbox mix starts at roughly 33% Google Workspace, 33% Microsoft 365, 33% SMTP, then auto-balances toward whatever performs for the customer's targets.
- Each plan bundles send credits, contacts-reached credits, verification credits (3× sends) and AI copy credits (5× sends). Monthly credits roll over up to 2x the monthly allocation; annual plans grant the full year upfront and expire at term end; credits expire at the end of the billing cycle after cancellation.
- Existing domains are never required or imported, because domains are provided free.
- Stated results: 97.4% inbox placement across the network over the trailing 30 days, 1.4x the reply rate of the same lists on legacy tools, 1M+ emails a day sent across the network.
- The app lives at https://app.senderpools.com; the public REST API is documented on ReadMe (https://sender-pools.readme.io).
- The Sender Pools MCP server (v1.6.0, 52 tools, Streamable HTTP) lets Claude, Cursor, Claude Code or any MCP client operate an account in plain English. Endpoint: https://api.senderpools.com/api/mcp. Setup: https://senderpools.com/mcp.

## Product

- [Sender Pools home](https://senderpools.com/): What the platform does, the free-infrastructure model, and the four-step flow (upload ICP, mailboxes built, warm/write/send/verify, rotate what underperforms).
- [Pricing](https://senderpools.com/pricing): Per-send pricing slider from 2k to 1M+ sends/month, what each plan includes, a cost comparison against per-mailbox tools, and the pricing FAQ (credits, rollover, unlimited mailboxes, fair use, warmup, deliverability, cancellation).
- [FAQs](https://senderpools.com/faqs): Every question we get, answered in full: product, pricing and credits, domains and mailboxes, deliverability, comparisons, API and MCP, referrals. Each answer has a stable anchor for citing.
- [MCP server](https://senderpools.com/mcp): Connect Claude, Cursor or Claude Code to Sender Pools: install config, example prompts and the catalog of all 52 tools.
- [Refer a friend](https://senderpools.com/refer): Referral program - 1,000 credits to the friend on signup and 1,000 to the referrer, uncapped, no expiry.
- [Sign up](https://app.senderpools.com/_auth/register): Create an account and start sending.
- [Log in](https://app.senderpools.com/_auth/signin): Existing customer login.
- [Book a demo](https://savvycal.com/senderpools/demo): Live call with a deliverability expert.

## API and MCP

- [Sender Pools API reference](https://sender-pools.readme.io): REST API, bearer API key authentication.
- [MCP server endpoint](https://api.senderpools.com/api/mcp): Streamable HTTP; tools only, no resources or prompts.

## Deliverability and infrastructure guides

- [How many mailboxes do you need for cold email? A sizing formula](https://senderpools.com/blog/how-many-mailboxes-for-cold-email): A step-by-step formula for sizing cold email infrastructure: daily volume, safe sends per mailbox, domains per mailbox and the buffer you actually need.
- [Email warmup in 2026: what actually moves inbox placement](https://senderpools.com/blog/email-warmup-2026): What email warmup does and does not do for cold email deliverability in 2026, how long it takes, and why it has to continue after the mailbox goes live.
- [Secondary domains for cold email: how to buy, configure and rotate them](https://senderpools.com/blog/secondary-domains-for-cold-email): Why cold email should never run on your main domain, how to choose and configure secondary domains, and how to rotate them so reputation damage stays contained.
- [How to Setup SPF, DKIM and DMARC For Cold Emails](https://senderpools.com/blog/how-to-setup-spf-dkim-and-dmarc-for-cold-emails): How to set up SPF, DKIM and DMARC for cold email: what each record does, how to create them, whether you need both SPF and DKIM, and why DMARC can fail anyway.
- [Maximizing Your Reach with Email Blasts: Strategies For Success](https://senderpools.com/blog/maximizing-your-reach-with-email-blasts-strategies-for-success): What an email blast is, how to set up and time a campaign, and how to measure results so bulk sends reach more inboxes without damaging your sender reputation.
- [Writing Effective Cold Email Messages: Everything You Need To Know In 2025](https://senderpools.com/blog/writing-effective-cold-email-messages-everything-you-need-to-know-in-2025): How to write effective cold emails in 2025: why they still work, a five-step process from research to subject lines, and answers to common cold email questions.

## Comparisons

- [Smartlead vs Instantly vs Sender Pools: the real cost of cold email infrastructure](https://senderpools.com/blog/smartlead-vs-instantly-vs-sender-pools-cost): What Smartlead, Instantly and Sender Pools each charge for, what you still buy separately, and how the total cost of cold email changes with volume.

## Cold email playbooks

- [A Guide To Email Preheaders - Benefits and Best Practices](https://senderpools.com/blog/a-guide-to-email-preheaders---benefits-and-best-practices): What an email preheader is, why preview text lifts open rates, the ideal preheader length, and best practices for pairing preheaders with subject lines.
- [Cold Email Follow Up Strategies - Steps To Success](https://senderpools.com/blog/cold-email-follow-up-strategies-steps-to-success): Why following up on cold emails wins most replies, how long to wait between touches, when to stop, and the rules of a cold email follow-up sequence that converts.
- [Cold Email Subject Lines For B2B Sales - Best Practices](https://senderpools.com/blog/cold-email-subject-lines-for-b2b-sales---best-practices): How to write cold email subject lines for B2B sales that get opened: why they matter, proven formulas, mistakes to avoid and examples you can copy.
- [Essential Guide: Email Signature Best Practices for 2025](https://senderpools.com/blog/essential-guide-email-signature-best-practices-for-2025): What to include in a professional email signature, the extras worth adding, and design best practices so your signature builds trust and stays out of spam.
- [How Cold Email Works](https://senderpools.com/blog/how-cold-email-works): How cold email works: what makes it different from newsletters and spam, whether it is legal, the types of cold emails, and the structures that get replies.
- [How To Send a Video Through Email - Everything You Need To Know](https://senderpools.com/blog/how-to-send-a-video-through-email---everything-you-need-to-know): Four ways to send a video through email, how to use video in newsletters and cold outreach, and tips to keep deliverability high when you embed or link video.
- [How to Send Bulk Cold Emails with 50%+ Open Rates](https://senderpools.com/blog/how-to-send-bulk-cold-emails-with-50-open-rates): A step-by-step playbook for bulk cold emails with 50%+ open rates: list building, verification, personalization, spintax, sender rotation and sequencing.
- [How to Use Spintax for Bulk Cold Emails Effectively](https://senderpools.com/blog/how-to-use-spintax-for-bulk-cold-emails-effectively): What spintax is, how the {a|b|c} format and nested spintax work, why it protects deliverability, and how to use it in bulk cold email without sounding robotic.
- [Is Email Case Sensitive? Setting The Record Straight](https://senderpools.com/blog/is-email-case-sensitive-setting-the-record-straight): Are email addresses case sensitive? What the standards say about capital letters and special characters in an address, and what it means for deliverability.
- [P.S. In An Email: How To Use Correctly](https://senderpools.com/blog/p-s-in-an-email-how-to-use-correctly): What P.S. means, how to use a postscript in an email correctly, why it is one of the most-read lines in cold outreach, and examples you can borrow.
- [Prospecting vs Lead Generation: Understanding Their Differences](https://senderpools.com/blog/prospecting-vs-lead-generation-understanding-their-differences): Prospecting vs lead generation: how the two differ, when to use each, and examples of prospecting and lead generation cold emails that fill a B2B pipeline.
- [Send Cold Email Without Getting Blocked](https://senderpools.com/blog/send-cold-email-without-getting-blocked): Why cold emails get blocked, how to set up your account and domains to avoid it, and how many emails you can send per day without getting blacklisted.
- [The Best Time To Send An Email To Cold Prospects And Boost Your Success](https://senderpools.com/blog/the-best-time-to-send-an-email-to-cold-prospects-and-boost-your-success): The best days and times to send cold emails to prospects, why timing affects open and reply rates, and what to weigh when scheduling your campaigns.
- [The Ultimate Guide to Overcoming Common Sales Objections](https://senderpools.com/blog/the-ultimate-guide-to-overcoming-common-sales-objections): The most common B2B sales objections you'll hear after a cold email, how to categorize them, and a step-by-step process for handling and overcoming each one.
- [Understanding Gmail's Sending And Recipient Limits](https://senderpools.com/blog/understanding-gmails-sending-and-recipient-limits): Gmail's daily sending and recipient limits for free and Google Workspace accounts, what happens when you hit them, and how cold emailers get around them.
- [Using Cold Email for Lead Generation: Everything You Need To Know](https://senderpools.com/blog/using-cold-email-for-lead-generation-everything-you-need-to-know): How to use cold email for lead generation: build an ideal customer profile, write a message that gets replies, analyze results and optimize your campaigns.
- [What Affects Email Open Rates? A Deep Dive](https://senderpools.com/blog/what-affects-email-open-rates-a-deep-dive): What email open rates measure, what counts as a good average, how to calculate open rate and click-to-open ratio, and what pushes open rates up or down.

## Optional

- [Blog index](https://senderpools.com/blog): All 24 articles, filterable by deliverability, infrastructure, cold email, guides and comparison.
- [Full text for assistants](https://senderpools.com/llms-full.txt): Every FAQ, the pricing table, the MCP tool catalog and every article in one Markdown file.
- [Privacy policy](https://senderpools.com/privacy)
- [Terms of service](https://senderpools.com/terms)