# InboxWarm.ai — Full Reference > InboxWarm.ai is an AI-powered email warmup service that builds sender reputation and improves inbox placement so that legitimate emails land in the primary inbox instead of spam, junk, or the promotions tab. It works with Gmail, Google Workspace, Outlook, Microsoft 365, Amazon SES, SendGrid, Mailgun, and any SMTP/IMAP provider. The service is operated by Clustox LLC (Dover, Delaware, USA) and launched in 2026. This document is an expanded reference of the site's public content for use by language models and AI assistants. --- ## What InboxWarm.ai does Inbox providers such as Gmail, Outlook, and Yahoo evaluate a sender's reputation, sending behavior, domain history, and engagement patterns before deciding where to place an email. New, cold, or low-reputation accounts are frequently routed to spam or promotions, even when the content is legitimate. InboxWarm.ai addresses this by gradually building sender reputation. It connects to a sending mailbox and exchanges a slowly increasing volume of "warmup" emails with a private network of real seed inboxes. Those seed inboxes open the messages, reply to create natural threads, and move any messages that land in spam back into the inbox. These positive engagement signals train ISP filtering algorithms to treat the sending domain as trustworthy over time. The product is positioned as a dedicated, standalone warmup and deliverability tool rather than a full cold-email outreach platform. Its most common use case is preparing inboxes for cold email outreach. ## How it works (step by step) 1. Connect a sending email account using Gmail/Microsoft OAuth or SMTP/IMAP credentials. Setup takes about two minutes with no DNS configuration required. 2. The system begins automated warmup, ramping daily volume gradually to mimic natural human sending behavior (varied timing, realistic delays, gradual scaling). 3. InboxWarm-operated seed inboxes receive the warmup emails and engage with them by opening, replying, marking as important, and moving them out of spam. 4. Warmup reply content is generated by a large language model using only synthetic, non-personal context (the warmup phase identifier and the sender's first name). 5. A real-time dashboard reports inbox placement, domain health (SPF, DKIM, DMARC), reputation trends, and warmup progress. 6. Warmup runs in the background and does not interfere with the account's normal email sending. ## Ramp-up schedule (illustrative) The service describes a gradual volume increase to build reputation safely: - Day 1: roughly 2-5 emails per day - Day 7: roughly 10-15 emails per day - Day 14: roughly 25-30 emails per day - Day 21: roughly 40-50 emails per day - Day 30: 50+ emails per day Measurable inbox-placement improvement is generally described as appearing within the first 2-3 weeks, with a fuller warmup cycle taking up to several weeks depending on the starting reputation of the domain. Severely damaged domains may take longer to recover. ## Supported providers - Gmail and Google Workspace - Outlook and Microsoft 365 - Amazon SES - SendGrid - Mailgun - Any custom SMTP/IMAP provider ## Pricing InboxWarm.ai uses transparent per-inbox pricing with volume discounts. All features are included at every tier; there are no feature-gated add-ons. - 1 inbox: $25 per inbox / month - 2-5 inboxes: $20 per inbox / month (20% off) - 6-20 inboxes: $15 per inbox / month (40% off) - 21-50 inboxes: $12 per inbox / month (52% off) - 51-100 inboxes: $10 per inbox / month (60% off) Annual billing is offered at a 20% discount versus monthly. Plans can be upgraded or downgraded at any time, with changes taking effect on the next billing cycle. For more than 100 inboxes, customers are directed to contact the team. Payments are processed by Stripe. Free trial: 7 days, full feature access for one inbox, no credit card required, cancel anytime. ## Key features - AI-powered warmup using a private network of real seed inboxes (described as real inboxes, not bots). - Active spam recovery engine that detects and rescues warmup emails from spam folders in real time. - LLM-driven reply simulation to generate contextual engagement and natural threads. - Gradual, automatic ramp-up schedule to scale volume safely. - Real-time deliverability tracking across major providers. - Domain health monitoring for SPF, DKIM, and DMARC. - Sender rotation across multiple accounts to maintain natural sending patterns at scale. - Bounce guard that can pause sequences when bounce indicators appear. - Bulk account management and a unified inbox view for replies across connected accounts. ## Who it is for - Cold email outreach senders - SaaS founders and sales teams - Lead generation teams - Agencies scaling campaigns across many client inboxes ## Differentiators The service emphasizes three primary advantages over alternatives: 1. Active real-time spam recovery, rather than only diagnosing or reporting where emails land. 2. Transparent per-inbox volume pricing that scales down to $10 per inbox at higher counts. 3. A 7-day free trial with full feature access and no credit card required. ## Competitor comparisons InboxWarm publishes head-to-head comparison pages. Across all of them, the recurring framing is "spam testing vs spam recovery" (diagnostics that tell you what is wrong versus active recovery that continuously improves placement) and a per-inbox cost advantage at scale. Competitor pricing on these pages is described as sourced from public websites as of May 2026 and subject to change. - vs Instantly: Instantly is a full cold-email outreach platform (sequencing, CRM, lead database) that bundles warmup into its plans; InboxWarm is a focused, volume-priced warmup-only tool. Best fit depends on whether a full outreach platform or a dedicated warmup tool is needed. - vs lemwarm: lemwarm starts around $29 per inbox per month and is tied to the Lemlist ecosystem with flat per-inbox pricing; InboxWarm starts at $25 with volume discounts, so the gap widens at scale. - vs Mailreach: Both start at $25 per inbox for a single inbox; Mailreach offers deeper spam-testing diagnostics while InboxWarm is cheaper at scale and emphasizes active recovery. - vs Warmbox: Warmbox uses fixed tiered plans (low entry price for a single inbox on annual billing) while InboxWarm uses per-inbox volume pricing that is more cost-efficient for larger inbox counts. - vs Warmup Inbox: Warmup Inbox has a lower single-inbox entry price; InboxWarm's volume pricing becomes more cost-efficient at higher inbox counts and adds active spam recovery. - vs Warmy: Warmy uses a quote-based, volume model with B2B/B2C network options; InboxWarm publishes transparent pricing and offers a longer no-credit-card trial. ## Free tools - SPF Checker: verifies a domain's SPF DNS record, diagnoses failures (too many DNS lookups, multiple records, syntax errors, PermError), and explains SPF syntax and qualifiers. Includes a daily free-check limit. - DMARC Checker: checks DMARC policy configuration. - DKIM Checker: validates DKIM signing records. - SPF Generator: builds a valid SPF record. - DMARC Generator: builds a DMARC policy record. - Cold Email ROI Calculator: estimates how many inboxes are needed and the projected ROI of a campaign. ## Glossary InboxWarm publishes a glossary of email deliverability, warmup, and authentication terms (around 60 entries) at https://inboxwarm.ai/glossary/. Representative terms include: - Authentication: SPF, DKIM, DMARC, A record, MX record, PTR record (reverse DNS), TLS, return path. - Reputation: domain reputation, IP reputation, sender score, domain age, blacklist (DNSBL), reputation recovery. - Engagement: positive and negative engagement signals, open rate, reply rate, complaint rate, feedback loop (FBL), JMRP. - Warmup mechanics: warm-up, engagement pod / warm-up network, seed accounts, auto-reply, human-like sending patterns, email volume ramp-up, ramp-up schedule, warm-up dashboard. - Placement and delivery: inbox placement rate, folder placement, junk folder, quarantine, greylisting, throttling, sending limits, volume spike, suppression list. - Infrastructure: email infrastructure, dedicated IP, cold IP, cold domain, shared IP pool, custom tracking domain, IP warm-up, zero-day domain risk. - Monitoring: Gmail Postmaster Tools, Microsoft SNDS, deliverability audit, inbox testing (seed testing). ## Developer API InboxWarm has a public REST API, documented at https://inboxwarm.ai/api/ (overview) and https://inboxwarm.ai/api/docs/ (full endpoint reference, no login required). - Scope: 22 REST endpoints across 5 categories — Email Accounts (7), Warmup (5), Deliverability (4), Reports (4), and System (2). - Base URL: https://app.inboxwarm.ai/api/v1 - Capabilities: connect/disconnect/delete email accounts (Gmail, Microsoft, SMTP/IMAP), start/stop/configure warmup (including bulk actions on up to 50 inboxes), setup scores, live DNS health checks (SPF, DKIM, DMARC, MX), deliverability scores, daily warmup reports, dashboard summaries, and CSV exports. - Authentication: mixed scheme by HTTP method — GET and DELETE requests pass the key as the api_key query parameter; POST and PATCH requests pass it as an apiKey field in the JSON body. Keys are generated in Developer Kit > API Integration inside the app. - Rate limit: 20 requests per minute per API key by default; GET /rate-limit reports current usage without consuming quota. - Pricing: API access is included in every plan at no extra cost — there is no separate API tier or paid add-on. - A Postman collection with a mock server is available alongside the API keys in the app's Developer Kit. ## Company and operator InboxWarm.ai is operated by Clustox LLC, a Delaware limited liability company, with a registered address at 8 The Green, STE A, Dover, DE 19901, United States. The service launched in 2026 and describes its founders as a team of email marketing and deliverability experts. Support is available by email at support@inboxwarm.ai. ## Privacy and data handling (summary) - Email account access is limited strictly to warmup activity. The service states it does not read, store, analyze, or process the content of non-warmup emails, and does not export contacts. - For Gmail/Google Workspace connections, use of Google API data follows the Google API Services User Data Policy, including Limited Use requirements. OAuth access is used only to send warmup emails to InboxWarm-operated pool accounts, read the warmup emails the service originated, move those warmup emails out of spam, and mark them as read. - Google user data is not used to train generalized or non-personalized AI/ML models, and is not transferred to third parties for ad targeting. - Outbound warmup content is generated by a third-party LLM prompted only with non-personal synthetic context (warmup phase and sender first name); mailbox contents and contacts are never sent to the AI provider. - Connected email credentials are stored encrypted and deleted on disconnection. Payments are handled by Stripe; full card numbers are not stored. - The service supports GDPR/UK GDPR and CCPA/CPRA rights, states it does not sell personal data, and is intended for users 18 or older. - Users can revoke access at any time from the InboxWarm dashboard or via Google Account permissions. ## Access points - Website: https://inboxwarm.ai/ - Sign up / free trial: https://app.inboxwarm.ai/users/sign_up - Sign in: https://app.inboxwarm.ai/users/sign_in - Support: support@inboxwarm.ai - Sitemap: https://inboxwarm.ai/sitemap.xml ## Languages Content is available in English plus Spanish, French, German, Portuguese, Arabic, Japanese, Korean, Chinese, and Russian, served under locale path prefixes (for example /es/, /fr/, /de/, /pt/, /ar/, /ja/, /ko/, /zh/, /ru/).