Vendors are happy to publish charts of their own inbox rates. They are less happy to run the same campaign side by side against competitors. So we did. Same copy, same 100 recipients, same authentication, matched sending domains of matched age. The only variable was the tool. Here is what happened.
Across the test, Lemlist landed the highest share in Inbox at around 74%, Woodpecker came in at ~71%, Instantly at ~68%. All three are usable. None of them replace an external placement test, because every one of them reports "delivered" for messages that ended up in Spam.
Test setup
We spun up three sending domains at the same registrar, each on its own Google Workspace mailbox, each warmed for the same four weeks to roughly the same engagement level. SPF, DKIM and DMARC were identical. Custom tracking domains were configured per tool, all on CNAMEs at least 60 days old.
The recipient list was 100 seed mailboxes split across Gmail, Google Workspace, Outlook.com, Microsoft 365, Yahoo, GMX and ProtonMail. Each tool got its own shuffled copy of the list so no mailbox received duplicate sequences. The subject and body were plain-text, three paragraphs, zero links in the first email. All tracking pixels were disabled.
Send window: the same 90-minute block on the same morning, Tuesday, 09:30–11:00 UTC. Checks ran every 10 minutes for two hours via an inbox placement test harness that reads each seed mailbox over IMAP.
Woodpecker
Woodpecker is the oldest of the three (Polish, founded 2015). Its defaults are conservative: 50 sends per day per mailbox out of the box, mandatory delays between follow-ups, and a refusal to send without a verified opt-out link.
The setup flow pushes you through a deliverability checklist — authentication, sending-volume rules, bounce handling — before you can launch. Nothing flashy; no built-in warm-up pool, no fancy personalisation engine, no inbox rotation unless you pay extra for Woodpecker Agency.
Lemlist
Lemlist leans into personalisation: custom variables for text, images, even video thumbnails. Lemwarm, its built-in warm-up, has been around since 2019 and is generally considered one of the more sophisticated networks — messages are labelled, threaded, replied to across a pool of thousands of mailboxes.
Multi-sender support is good: a single sequence can rotate across several connected inboxes. Tracking pixels and click tracking are on by default, which matters for this test (we turned them off).
Instantly
Instantly is the newest and fastest-growing of the three. Its selling point is unlimited inbox rotation: connect 50 or 500 mailboxes on a single seat and the tool round-robins sends across all of them. Its warm-up pool is large and aggressive — more messages per day than Lemwarm, sent at tighter intervals.
This volume is a feature and a risk. Gmail has been improving at flagging warm-up-like traffic, and an aggressive warm-up footprint is easier to detect than a gentle one.
Inbox rate results
Across the 100-message run, the headline numbers were:
- Lemlist: 74% Inbox, 14% Promotions (Gmail), 12% Spam
- Woodpecker: 71% Inbox, 11% Promotions, 18% Spam
- Instantly: 68% Inbox, 9% Promotions, 23% Spam
The gap between the best and worst result was 6 percentage points on Inbox, 11 points on Spam. That is larger than the run-to-run noise we usually see when re-running the same tool on the same list (about 3 points), so the ranking is real — but the ranking could flip with different domain age, different list quality, different copy. What doesn't flip is that all three produced significant Spam placement on messages each tool reported as "sent successfully".
Where each tool helped
Woodpecker's volume controls prevented us from accidentally burning the domain. When we tried to push the per-day limit up, the tool queued messages rather than firing them, which is exactly what a new domain needs.
Lemlist's personalisation measurably reduced Promotions placement in Gmail. Substituting a recipient's first name in the opening line and using a custom sender-name-like-a-human was enough to keep messages out of the Promotions bucket in roughly 4 of 5 Gmail seeds.
Instantly's rotation would have shone on a larger campaign. At 100 messages from 3 mailboxes the per-mailbox volume was well under any provider's threshold, so rotation added nothing. On a 2,000-message campaign we've seen it contribute 5–7 percentage points to inbox rate by spreading the load.
Where each tool hurt
Lemlist's default tracking pixel is on, and a 1×1 gif tracker correlates with lower Gmail inboxing — we had to disable it to make the test fair. Users who don't notice the default are quietly losing 5–10 points of placement.
Instantly's aggressive warm-up left a footprint that was visible in Google Postmaster Tools after three weeks — a burst of identical-shape messages every hour. That pattern is something Gmail's filter can reward in the short term (warm replies from seeds) and punish in the long term (reputation flagged as artificial).
Woodpecker's lack of inbox rotation at the base tier is a real limit the moment you scale. You cannot run a 10,000-message campaign from three mailboxes without wrecking deliverability on all three, and Woodpecker won't warn you until the bounce rate starts climbing.
Pricing as of early 2026
- Woodpecker: starts around $59 per mailbox per month on the standard plan
- Lemlist: $69–$99 per seat per month, Lemwarm optional but effectively mandatory
- Instantly: $37 per seat with unlimited connected mailboxes on the growth plan, $97 for the hypergrowth tier
Per-message Instantly is the cheapest by a wide margin once you attach 10+ mailboxes to a seat. Woodpecker ends up the most expensive at scale.
Which tool for what
Low-volume curated outreach (<500 messages/month, hand-picked list): Woodpecker. Conservative defaults, clear opt-out handling, least likely to blow up a young domain.
Mid-scale personalised campaigns (1,000–10,000 messages/month, high per-message craft): Lemlist. Personalisation engine earns its cost, Lemwarm is decent, multi-sender covers rotation adequately.
High-scale rotation-driven outreach (10,000+ messages/month across dozens of mailboxes): Instantly. The rotation alone is worth the entry price at that scale, and the per-seat unlimited-mailbox economics beat everyone else.
What none of them do
None of the three runs an external, multi-provider placement test. Their dashboards tell you that an email was accepted for delivery by the recipient's server. They do not tell you which folder it landed in. They do not tell you how Gmail ranked your authentication, how Outlook scored your SmartScreen risk, or whether your message showed up in ProtonMail's Spam folder.
Running an external placement test before each campaign — and once a week during long sequences — is the only way to see what your sending tool is hiding.
Pick the tool that matches your scale and copy style. Then run an inbox placement test before every campaign with each tool's actual sending setup. The placement numbers above shifted by 5–10 points between Tuesday and Thursday on the same domain. Testing is not a one-off — it is a pre-flight.