# What Is Email Warmup? How It Works, How Long It Takes, and How to Do It URL: https://warmerly.com/email-warmup Published: 2026-04-02 (updated 2026-09-29) > What email warmup is, the signals Gmail and Outlook score, how long it takes (7 to 28 days), and step-by-step guides for Gmail, Outlook and new domains. Email warmup is the process of building a sending mailbox's reputation before you use it for cold outreach: the mailbox exchanges a small, slowly rising volume of real conversations with other mailboxes, which open them, reply to them, and rescue them from spam. Those actions show Gmail and Outlook that the address belongs to a sender people want to hear from. A new domain needs 21 to 28 days of it before any cold email; an aged, clean domain needs 7 to 10. ## Why mailbox providers need to see warmup Gmail and Microsoft decide where your mail lands from how recipients have treated mail from your domain before. A new domain has no history, so it is treated as suspicious by default. Send 50 cold messages on day one and you trip every bulk-sender heuristic at once: the mailbox is flagged, and almost everything it sends afterwards is filtered. The damage does not stay with the mailbox. Negative reputation attaches to the sending domain, so every other mailbox on it inherits the filtering. A burnt domain rarely recovers fully; most senders register a new one and start again, and if they skip warmup a second time they burn that one too. ## How email warmup works Warmup software (Warmerly included) connects your mailbox to a network of other real mailboxes. Through the day your mailbox sends a few short, conversational messages to peers; the peers open them, mark them important, reply to them, and move them out of spam if they land there. Volume starts at a handful a day and rises as the mailbox earns trust. *Figure: Illustration: a mailbox exchanging warmup mail with a pool of other verified mailboxes, which open, reply to and rescue each message.* Not every action counts the same. The signals that move reputation in 2026, roughly in order of weight: 1. Spam-folder rescue. A recipient moving your message out of spam and into the inbox is the strongest positive signal Gmail tracks. Many warmup tools skip it; Warmerly does it on every peer. 2. A reply with quoted history. A real reply that quotes the original message is what people actually do, and filters reward it well above an open. 3. Star, label, mark important. Explicit user actions people take on mail they care about. 4. Open. Worth less than it used to be (Apple Mail Privacy Protection makes opens noisy), but still positive. 5. Cross-provider engagement. Gmail peers replying to Outlook senders and the other way round builds reputation at both providers, which is why the peer mix matters. > **What warmup cannot do** — Warmup builds the reputation layer and nothing else. It cannot rescue a domain without SPF, DKIM and DMARC, an unverified list with a 10% bounce rate, or copy people mark as spam. Fix those first, then warm. ## How long email warmup takes Domain age decides most of it. A brand-new domain (under 30 days old) needs 21 to 28 days of warmup before any cold mail. A domain 30 to 180 days old with light use needs 14 to 18. A domain older than six months with a clean history can be ready in 7 to 10. A previously burnt domain needs 30 days at minimum and often never fully recovers. Calendar days are only a guide. A mailbox is ready when its health score has held above 80 for three days, seed tests show 95% or better inbox placement at the provider your prospects use, and the spam-rescue rate is falling because fewer messages land in spam to begin with. The full timeline, with the ramp that follows it, is in the chapter on how long warmup takes. ## Warmup by provider The mechanics are the same everywhere; what each provider weighs, and the tool you check it with, is not. - Gmail weighs domain reputation above everything, reacts to a complaint spike within 24 to 48 hours, and takes weeks to forgive it. Google Postmaster Tools shows where you stand. - Google Workspace runs on Google's servers, but that buys you nothing with the spam filter: reputation belongs to your domain, which starts at zero. DKIM has to be switched on in the Admin Console. - Outlook and Microsoft 365 filter through Exchange Online Protection, which gives IP reputation nearly equal weight to domain reputation and treats 1024-bit DKIM keys as weak. SNDS and JMRP are the monitoring tools. ## The mistakes that burn a domain during warmup - Warming your main business domain. Use a separate sending domain, so a mistake costs you an outreach domain and not your company's email. - Skipping the DNS work. SPF, DKIM and DMARC must pass before warmup starts; warmup on a misconfigured domain is wasted time. - Sending cold mail mid-warmup. Even a small cold batch resets progress and can flag the mailbox. - A peer network made only of other new mailboxes. Closed loops of fresh accounts are detected within days; the pool needs aged, healthy mailboxes in it. - Stopping warmup when campaigns start. Reputation decays in quiet weeks, so warmup keeps running at reduced volume for as long as the mailbox sends. ## Warmup by hand, or with a tool You can warm a mailbox by hand, by trading a few emails a day with colleagues and friends who reply and rescue your mail from spam. It works for one mailbox for two weeks and falls apart after that: nobody keeps it up at 40 messages a day across a mixed-provider pool, and nobody runs it quietly for months alongside campaigns. A warmup tool automates the cadence, the ramp and the rescue. Warmerly's plans are flat per workspace rather than per mailbox: free for one mailbox, $19 a month for 5 and $49 for 25, with warmup on every mailbox, daily SPF, DKIM and DMARC checks, and campaign sending with no cap. If you are comparing options, the chapter on the best warmup tools prices 14 of them side by side. ## Where to start Today: publish SPF, DKIM and DMARC, register a separate sending domain if you have not, and start warming the mailboxes you intend to send from. Then read the chapter that matches your setup: a new domain, Gmail, Google Workspace or Outlook. ## Questions ### What is email warmup in simple terms? Email warmup is gradually building a new mailbox's sending reputation by exchanging a small, rising volume of real conversations with other mailboxes that open, reply to and rescue your messages from spam. It teaches Gmail and Outlook that your address is a sender people engage with, before you send cold email from it. ### Is email warmup still necessary in 2026? Yes, for any new or long-quiet domain that will send cold or bulk email. Gmail, Yahoo and Microsoft all filter new senders heavily and require SPF, DKIM and DMARC from bulk senders. A domain with no engagement history is treated as suspicious until it has one. ### How long does email warmup take? 21 to 28 days for a brand-new domain, 14 to 18 for a domain 30 to 180 days old, and 7 to 10 for an aged domain with a clean history. The real signal is readiness, not days: a health score above 80 for three days and 95% inbox placement in seed tests. ### Can I warm up a personal @gmail.com or @outlook.com address? Not meaningfully. Warmup builds the reputation of a domain you control, with SPF, DKIM and DMARC records you publish. A personal address on a shared consumer domain has none of those, so cold outreach should come from a custom domain on Google Workspace, Microsoft 365 or another mail host. ### Should warmup keep running after campaigns start? Yes, at reduced volume (roughly 20 to 30% of its peak). Reputation decays during quiet periods, and ongoing warmup offsets the occasional bounce or complaint from real campaigns. A gap of more than two weeks usually needs a short re-warm before campaigns resume. ### How much does email warmup cost? Per-mailbox tools charge roughly $15 to $70 per mailbox per month. Flat-rate tools cost less once you have more than one mailbox: Warmerly is free for one mailbox, $19 a month for 5 and $49 for 25, with warmup included on every mailbox. --- Source: https://warmerly.com/email-warmup Full content index: https://warmerly.com/llms-full.txt Site index: https://warmerly.com/llms.txt