Campaigns Sequences · mailbox pools · auto-promoting A/B

Multi-step sequences that pick their own winner.

Build a sequence, point it at a pool of mailboxes, and let it run. NuMail rotates every send across your inboxes, schedules each touch for the lead's local morning, and runs the A/B test for you — promoting the winning variant the moment it crosses significance.

Start free trial →See the sub-features
▸ Sequence builder

Steps, delays, variants.

A sequence is an ordered list of steps. Each step has a delay, a subject, a body, and — if you want — competing variants. Personalize with merge fields; the engine handles the rest.

Compose once. Run for months.

Drag steps into order, set the gap between each, and write your copy with {{first_name}}-style merge fields. Follow-ups thread onto the original send, so they land as Re: in the same conversation.

  • Steps per sequence Up to 12
  • Delay precision Hours or days
  • Variants per step Up to 5
  • Merge fields Any lead column
  • Auto-stop on reply Per campaign
  • Threading Re: into one thread
Q2 outbound · cohort BActive
1
Day 0 · on enroll
Quick q on {{company}}
Hey {{first_name}} — noticed you're hiring SDRs. Are you running outbound in-house or…
2
winner
VARIANT A
Re: {{company}}
reply 9.2%
VARIANT B
Worth a look?
reply 5.1%
3
Day 7 · if no reply
Re: {{company}}
Last nudge from me — happy to send the 2-line teardown if it's useful, otherwise I'll get out of…
▸ What's in a campaign

Six things, working together.

Every campaign ties the same primitives into one running system — so you set it up once and it keeps optimizing itself.

Sequence builder

Order multi-step touches, set delays in hours or days, thread follow-ups onto the original send, and auto-stop a lead the moment they reply.

up to 12 steps
🗂

Mailbox-pool rotation

Assign a pool, not a single inbox. Sends rotate across every healthy mailbox, respecting each one's daily cap, warmup tier, and sending window.

volume without burnout
📊

Statistical A/B + auto-promote

Run variants on subject or body. NuMail tracks reply lift, computes significance, and promotes the winner automatically once the threshold is reached.

no manual call
🕐

Per-lead scheduling

Each touch fires in the lead's own local morning, not yours. Set send windows and working days per campaign; weekends and holidays are skipped.

their timezone
🔗

Lead lists & CRM sync

Import a CSV with column-mapping suggestions, or sync a HubSpot list two ways — new contacts enroll automatically, replies and bookings write straight back.

HubSpot two-way
📈

Live campaign analytics

Real-time funnel from enrolled → sent → opened → replied → booked, broken out per step, per variant, and per mailbox. Export or pull it from the API.

per step · per mailbox
▸ Mailbox-pool rotation

One campaign. Many mailboxes.

Sending a million emails a month from one inbox gets you blocked. NuMail spreads the load across a pool — and never asks a mailbox to do more than it safely can.

The pool throttles itself.

Point a campaign at a pool of mailboxes and the engine round-robins every send across them. It reads each mailbox's daily cap, current warmup tier, and sending window — and routes around any inbox that's paused, throttled, or showing a reputation dip.

Add a per-campaign throttle on top to pace overall volume, and a suppression list so a domain you've already contacted (or unsubscribed) is never touched again — across every campaign in the workspace.

A
amir@anchor-go.com
gmail · tier 4 · warm
42 / 50
S
sara@anchor-mail.io
m365 · tier 4 · warm
38 / 50
J
jon@anchor-hq.com
gmail · tier 3 · ramping
21 / 35
R
rob@anchor-team.co
smtp · paused · skipped today
0 / 50
Routed across 3 healthy mailboxes today101 sends
▸ Statistical A/B

It declares the winner so you don't have to.

Most tools split traffic and leave you eyeballing two numbers. NuMail runs the test properly — and acts on the result automatically.

Significance, then auto-promote.

Add variants to any step. The engine splits enrollment evenly, measures reply rate as the primary metric, and runs a continuous significance test as data lands.

  • Reply rate is the metric that matters — not opens
  • Waits for a real sample before calling anything
  • Promotes the winner to 100% the moment it's significant
  • Fires an ab_winner.declared webhook so your stack knows
  • Or flip off auto-promote and decide by hand
Step 2 · subject test95% significant
Variant A1,204 sent
winner
9.2%
Variant B1,198 sent
5.1%
✓ Auto-promoted Variant A · remaining leads now use subject_a
▸ Why this is better

Pooling and auto-promotion do the work.

The difference isn't features on a list — it's whether the system runs itself once it's live, or quietly waits on you.

The usual way

  • One mailbox per campaign — scaling means cloning the whole thing N times by hand.
  • You watch two A/B numbers and guess when one is "winning."
  • The losing variant keeps burning half your leads until you remember to switch.
  • Sends fire on your clock, hitting prospect inboxes at 3am their time.
  • Suppression is per-campaign, so the same domain gets emailed twice.

NuMail

  • One campaign, a whole pool — add mailboxes and volume scales with zero rework.
  • A continuous significance test calls the winner the instant the math supports it.
  • The winner auto-promotes to 100%, so no leads are wasted on the loser.
  • Every touch lands in the lead's local morning, on working days only.
  • Suppression is workspace-wide — a contacted or unsubscribed domain is off-limits everywhere.
We pointed one campaign at a 14-mailbox pool and turned auto-promote on. Two weeks later the engine had already swapped in the better subject line — we'd never have caught the lift that fast by hand.
Priya N · Head of Growth · running outbound across 6 clients

Set it up once.
Let it optimize itself.

Build a sequence, assign a pool, turn on auto-promote. NuMail handles rotation, scheduling, throttling, and the A/B — you watch the replies land.