Comparison, Tools, Warmup
Instantly vs Smartlead vs Warmerly: Which Email Warmup Tool Is Right in 2026
All three warm your mailboxes and send your campaigns. They differ on what they meter, how they handle LinkedIn, and how deep the deliverability tooling goes. Here is the honest comparison, including where we (Warmerly) lose.
Updated 10 min read
In this article
All three warm mailboxes and send cold email campaigns, and all three include warmup with unlimited or plan-sized mailboxes. The differences: Instantly ($47/month) is the best-known brand with the biggest ecosystem but caps its entry plan at 5,000 emails a month; Smartlead ($39/month) has the strongest API and caps entry at 6,000 emails; Warmerly ($19/month for 5 mailboxes) has no cap on campaign sends, native LinkedIn at $50 per account, and the deepest deliverability monitoring, but is younger with fewer integrations. Pick Smartlead to build on an API, Instantly for ecosystem and brand, Warmerly for flat pricing and deliverability.
We make Warmerly, so read this with that in mind. Competitor prices were read from Instantly's and Smartlead's pricing pages on 28 September 2026 at monthly billing, and the section on where Warmerly loses is meant seriously.
The summary table
| Instantly | Smartlead | Warmerly | |
|---|---|---|---|
| Entry price | $47/mo ($37.60 annual), Growth | $39/mo ($32.50 annual), Base | Free plan, then $19/mo (Starter) |
| Mailboxes on entry plan | Unlimited | Unlimited | 5 (Starter), 25 (Growth, $49), 100 (Agency, $179) |
| Warmup | Unlimited, included | Included | Included on every mailbox |
| Entry plan volume | 1,000 contacts, 5,000 emails/mo | 2,000 active leads, 6,000 emails/mo | 5,000 active prospects, unlimited campaign sends |
| Next tier | Hypergrowth $97: 25,000 contacts, 125,000 emails | Pro $94 | Growth $49: 25 mailboxes |
| Via Aimfox (separate tool) | Via a separate HeyReach account | Native, $50/mo per account | |
| WhatsApp steps | Check current features | Check current features | Yes, in the same sequence |
| API | Yes | Strongest of the three | On Agency |
| Deliverability monitoring | Warmup-focused | Warmup-focused | Placement tests across 5 providers, daily SPF/DKIM/DMARC/MTA-STS checks |
| Maturity and integrations | Largest ecosystem | Large, API-first | Youngest, fewest integrations |
Price: what each one meters
The three tools meter different things, and that decides which is cheapest for you. Instantly and Smartlead let you connect unlimited mailboxes but cap monthly emails and contacts: 5,000 emails and 1,000 uploaded contacts on Instantly Growth, 6,000 emails and 2,000 active leads on Smartlead Base. Warmerly does the opposite: it caps mailboxes per plan (5, 25 or 100) and does not cap campaign sends.
Cost by scenario
| Scenario | Instantly | Smartlead | Warmerly |
|---|---|---|---|
| Founder testing cold email, 1 mailbox, a few hundred sends | $47 | $39 | $0 (free plan: 1 mailbox, 100 campaign sends/mo) |
| 5 mailboxes, about 4,000 emails/mo | $47 | $39 | $19 |
| 20 mailboxes, about 20,000 emails/mo | $97 (Hypergrowth) | $94 (Pro; check its volume limits) | $49 (Growth) |
| Add one LinkedIn account | Plus an Aimfox subscription | Plus a HeyReach subscription | Plus $50 |
| 80 mailboxes for an agency | Hypergrowth or above, by volume | Pro or above, by volume | $179 (Agency, 100 mailboxes) |
At small scale Warmerly is the cheapest by a wide margin. At very high volume from a modest number of inboxes, the comparison narrows, because Instantly and Smartlead do not charge per mailbox. If you run 300 inboxes, a mailbox-capped plan is the wrong shape, and Instantly or Smartlead will fit better.
Warmup
All three run peer-to-peer warmup: your mailbox exchanges conversational mail with other mailboxes in a network, which open, reply, mark important and rescue messages from spam. Instantly and Smartlead both run large networks built up over years of customers. Warmerly's is the smallest because we are newest; we health-grade peers and quarantine poor ones, and Warmerly rescues mail from spam every 10 minutes.
In practice, all three will warm a healthy mailbox with correct authentication. Warmup quality differences matter less than whether your SPF, DKIM and DMARC pass and whether you ramp new inboxes slowly.
Campaign sending
All three ship a campaign engine with multi-step sequences, A/B variants, stop-on-reply and a unified inbox for replies. Instantly and Smartlead have sent cold email at scale for longer and connect to more third-party tools. Warmerly's engine adds LinkedIn and WhatsApp steps on the same timeline as email, and pre-launch checks that block a campaign with a missing merge variable instead of sending a broken first line to your list.
LinkedIn and multichannel
Neither Instantly nor Smartlead runs LinkedIn natively. Instantly routes LinkedIn through Aimfox; Smartlead has you connect a separate HeyReach account. Both work, but they mean a second subscription, a second set of limits and split reporting. Warmerly runs LinkedIn itself at $50/month per account, with a human-paced warmup ramp for new or quiet accounts. LinkedIn has no free trial and is charged immediately.
API and integrations
Smartlead's API is the most complete of the three, which makes it the natural pick for agencies building their own dashboards or client portals. Instantly has a broad set of integrations and the largest user community. Warmerly's API is on the Agency plan, and its integration list is shorter. If a specific integration is essential, check it before you move.
Deliverability monitoring
This is where Warmerly goes furthest. Inbox placement tests seed your mail across five providers so you see where it lands at Gmail, Outlook and others separately. SPF, DKIM, DMARC and MTA-STS are checked daily on every domain, with an alert and fix instructions when a record breaks. Instantly and Smartlead focus on warmup health and sending controls; if placement testing and DNS monitoring matter to you, check what each includes on your plan.
Why this matters: warmup builds reputation, but it does not tell you when something breaks. A teammate adds a second SPF record, a DNS move drops the DKIM key, or one domain lands on a blocklist, and every tool keeps reporting the campaign as sent. The earlier you hear about it, the fewer emails go to spam before you fix it. If you stay on Instantly or Smartlead, run a placement test and a DNS check at least weekly, and always after changing providers or DNS hosts.
Where Warmerly genuinely loses
- Younger product, fewer integrations. Instantly and Smartlead have been sending at scale for longer and connect to more tools.
- Smaller warmup network. It is health-graded, but smaller than Instantly's or Smartlead's.
- API only on Agency. Smartlead's API is stronger and more complete.
- Mailbox caps. At several hundred inboxes, unlimited-mailbox plans from Instantly or Smartlead fit better.
- LinkedIn has no trial. The email plans do; LinkedIn is charged from the start.
Where Warmerly wins
- Price at small and mid scale: $19 for 5 mailboxes, $49 for 25, with no cap on campaign sends.
- A real free plan: 1 mailbox and 100 campaign sends a month, no card.
- Native LinkedIn and WhatsApp steps in the same sequence, no second subscription.
- Deliverability depth: five-provider placement tests, daily authentication checks with fix instructions, spam rescue every 10 minutes.
Three questions that decide it
Most teams can choose in five minutes by answering three questions honestly.
- How many inboxes will you run in six months? Under 100, all three fit and Warmerly is cheapest. Several hundred, Instantly or Smartlead fit the shape better because they do not charge per mailbox.
- Is LinkedIn part of the plan? If every sequence needs a LinkedIn step, a native channel is simpler than a second subscription. If LinkedIn is occasional, a separate tool next to Instantly or Smartlead is fine.
- Will you build on the API? If you are wiring the tool into your own dashboards, client portals or data pipeline, start with Smartlead and check the endpoints you need before you commit.
A fourth question matters only if deliverability is already hurting: do you know where your mail is landing? If the answer is no, the tool with placement tests and daily DNS checks will save more than any price difference.
Switching between them
Sender reputation belongs to your domains and mailboxes at Gmail and Microsoft, so it moves with you. To switch, reconnect the same mailboxes to the new tool, turn warmup off in the old one so two networks are not warming the same inbox, export your leads with unsubscribes and bounces included, and rebuild sequences by hand. Run the first week at a lower daily volume and check placement before returning to full speed.
The honest recommendation
- Building custom tooling or client dashboards on an API: Smartlead.
- Hundreds of inboxes, the largest ecosystem and community: Instantly.
- Up to 100 mailboxes at a flat price, LinkedIn and WhatsApp in the same sequence, and the most deliverability monitoring: Warmerly.
- Already happy with a campaign tool: keep it, and use Warmerly for warmup and monitoring on the same mailboxes.
Frequently asked questions
Is Smartlead better than Instantly?
Smartlead is cheaper at entry ($39 against $47), allows more emails on its entry plan (6,000 against 5,000) and has the stronger API. Instantly has the larger ecosystem and community, and a clear upgrade path to 125,000 emails on Hypergrowth at $97. Both include warmup and unlimited mailboxes.
What is the cheapest alternative to Instantly and Smartlead?
Warmerly: a free plan with 1 mailbox and 100 campaign sends a month, then $19/month for 5 mailboxes with no cap on campaign sends, or $49 for 25. It is younger than both, with fewer integrations.
Do Instantly and Smartlead include email warmup?
Yes. Instantly includes unlimited warmup on Growth, and Smartlead includes warmup on Base. Warmerly includes warmup on every mailbox on every plan, including the free one.
Can Instantly or Smartlead do LinkedIn outreach?
Not natively. Instantly routes LinkedIn through Aimfox and Smartlead through a separate HeyReach account, each a second subscription. Warmerly runs LinkedIn natively at $50 per account per month, with no free trial.
Which has the best API: Instantly, Smartlead or Warmerly?
Smartlead's is the most complete of the three and the usual pick for agencies building their own dashboards. Check which Smartlead and Instantly plans include API access. Warmerly's API is on the Agency plan ($179/month for 100 mailboxes).
Can I use Warmerly alongside Instantly or Smartlead?
Yes. Keep Instantly or Smartlead as the sender and connect the same Gmail or Microsoft mailboxes to Warmerly for warmup, placement tests and daily SPF, DKIM and DMARC checks. Turn off warmup in the other tool first so two networks are not warming the same inbox.