Best email warmup tools
A new mailbox has no sending history, which is itself a red flag to spam filters. Warmup builds that history before real outreach starts.
Instantly wins for a team already sending through it, since warmup is included at no extra cost on every plan; a standalone warmup tool only earns its place for a mailbox sending through a platform that does not warm mailboxes itself.
The short answer
- Instantly includes unlimited email warmup on every Outreach plan, starting at $47/mo, with no separate warmup fee.
- Standalone warmup-only tools like Warmup Inbox charge per inbox per month, from $15/inbox/mo on the Basic tier to $79/inbox/mo on the Max tier, which adds up fast across a sender pool of a dozen or more mailboxes.
- Warmup works by exchanging realistic-looking mail with a network of other warmed inboxes, gradually increasing volume so a mailbox builds a normal-looking sending pattern before real outreach begins.
- The main reason to pay for a standalone warmup tool is sending through a platform, or a plain mailbox provider, that does not include warmup itself.
How we compared these
We compared whether warmup is bundled free into a sending platform versus sold as a standalone subscription, and what a standalone tool costs per mailbox. Facts checked on vendor pricing pages, September 2026.
We also checked what daily warmup volume each tier of a standalone tool actually supports, since a slow ramp on a cheap plan can take considerably longer to bring a mailbox to full sending capacity than a faster ramp on a pricier tier, which changes the real cost of getting a new domain ready to send at scale.
Email warmup comparison
| Tool | Starting price | Bundled or standalone | Cost model | Best for | Not for |
|---|---|---|---|---|---|
| Instantly | $47/mo Growth plan | Bundled into the sending platform | Unlimited warmup included on every plan, no per-mailbox fee | A team already sending cold outbound through Instantly | A team that sends through a different platform and only wants warmup |
| Warmup Inbox | $15/inbox/mo Basic (75 messages/day); $49/inbox/mo Pro (250/day); $79/inbox/mo Max (1,000/day) | Standalone, works with any mailbox provider | Per-mailbox monthly fee, tiered by daily warmup message volume | A mailbox sending through a platform with no built-in warmup | A team already on a platform with warmup bundled in; paying twice for the same job |
Figures checked on vendor pricing pages, September 2026, including warmupinbox.com/pricing.
The field, ranked
1. Instantly (bundled warmup)
Free on every plan starting at $47/mo, running on a large network of warmed accounts that exchange realistic mail automatically once a mailbox is connected. The obvious choice for anyone already sending through the platform, since there is no separate line item to track. Best for: a team that sends and warms from the same tool, with no extra setup. Not for: a team on a different sending platform without built-in warmup.
2. Warmup Inbox
Works with any mailbox regardless of sending platform, from $15/inbox/mo (75 messages a day) up to $79/inbox/mo (1,000 a day) depending on how fast the ramp needs to be. Best for: a mailbox sending through a plain provider or a platform without warmup built in, especially one that needs to be ready for volume quickly. Not for: a team already paying for bundled warmup elsewhere; paying for both is a wasted line item.
When none of these is the answer
A mailbox used only for internal team email, or for replying to inbound leads who already expect a message, does not need warmup; it never sends the kind of unsolicited volume that triggers spam filters in the first place. Warmup earns its place before a new mailbox joins a sender pool for genuine cold outbound.
The clearest example of the wrong fit is a company's primary domain mailbox that a founder uses for everything, sales replies, vendor emails, internal threads. That mailbox already has years of normal sending history and needs no warmup at all; running it through a warmup tool wastes money and, worse, mixes automated warmup traffic into an inbox real people rely on daily. Warmup belongs on new, dedicated secondary-domain mailboxes bought specifically for outbound, never on an established primary address.
Questions
- How long does warmup take before a mailbox is ready to send at volume?
- It varies with how aggressive the ramp is and the mailbox's starting reputation, but a commonly used pattern runs several weeks, gradually increasing daily volume, before pushing a new mailbox to full cold-outbound send levels.
- Is bundled warmup as good as a standalone warmup tool?
- For most teams, yes, since the mechanism, sending realistic mail to a network of other warmed inboxes, is similar across vendors. The main reason to pick a standalone tool is warming a mailbox that will send from a platform without its own warmup feature.
- Can warmup fix a mailbox that is already flagged?
- It can help rebuild reputation over time, but it is not a fast fix, and a severely burned domain is often better replaced than nursed back. Warmup works best as prevention before real sending starts, not as a rescue after damage is done. If a domain is already on a major blacklist, expect weeks of clean sending behavior before that reputation genuinely recovers, if it recovers at all.
- Does SalesCrew include warmup?
- Disclosure: SalesCrew is our product. It manages the sender pool and per-mailbox daily caps but does not run warmup itself; a new mailbox joining the pool should be warmed with a tool like these before it starts carrying real send volume.