Campaign Nucleus Competitive Intelligence
May 2026
ESP Default Sending Infrastructure

Custom domain is free.
The dedicated IP is where the industry charges.

A read across the ten most relevant email service providers shows a single, uniform onboarding posture: every major platform gives away custom domain authentication and uses a shared, pre-warmed default to get senders live in minutes. The monetization gate sits one layer deeper — at the dedicated IP, where prices range from $21 to $59 per month and serve as the field's clearest infrastructure upsell.

Prepared for    Campaign Nucleus Executive 10 Platforms · 4 Categories · Verified Q2 2026 Reading time · 6 min
§ 01 The lay of the land

Four numbers that frame everything.

If you remember nothing else from this brief, remember these. Each one is independently verified across all ten platforms surveyed.

Custom domain auth
$0
Universally free across all 10 providers. Not a revenue lever for anyone.
Dedicated IP spread
$21–59
Per month. The real upsell gate — a 2.8× spread across the field.
Default shared domain
8/10
Offer a pre-warmed shared sender at onboarding. SES and HubSpot Pro are the outliers.
Free daily send cap
100–300
The narrow band of the entry tier. Mailgun and SendGrid sit at the floor.

Read together, these four numbers tell you the whole story: onboarding is free, sending is rationed, and the dedicated IP is where every meaningful customer eventually ends up paying.

§ 02 The chart that matters

Dedicated IP pricing across the field.

The single visualization a C-level reader needs. Bars show monthly add-on price for a dedicated sending IP, the industry's primary infrastructure upsell. Dashed markers indicate platforms where dedicated IP exists but is not self-serve.

Dedicated IP — monthly add-on price

USD / month · self-serve where available
Amazon SES Infrastructure
Self-managedno upsell · usage only
Brevo Marketing
$21Pro+ only · $251/yr
SendGrid Infrastructure
$30Pro tier · +$30 ea extra
Mailgun Infrastructure
$59highest in field
ActiveCampaign CRM
Availablenot prominently priced
Mailchimp Marketing
Enterprisenot self-serve
Klaviyo Ecommerce
Enterprisenot self-serve
HubSpot CRM
Bundledafter $3–7K onboarding
Constant Contact Marketing
Not offeredno dedicated IP path
Omnisend Ecommerce
Not offeredno public pricing
$0 $15 $30 $45 $59
Self-serve price Pure-infra benchmark Not self-serve / not published
§ 03 The full matrix

All ten providers, side by side.

Filter by category to see how each cohort handles the same five decisions: default domain, free volume, custom domain pricing, dedicated IP, and the primary upsell lever.

View
Provider Default domain Free / entry volume Custom domain Dedicated IP Primary upsell lever
Mailchimp
Marketing-first
● Pre-warmed
Shared mc.com infra
500/mo · 250/dayFree tier · paid scales 10–12× contacts
● Free
DNS records only
Enterprise onlyNo published price
Automation gated behind $20+/mo Standard. Contact-count billing — unsubscribes still count. Actual bills run 20–40% over list.
Brevo
Marketing-first
● Pre-warmed
Falls to @brevosend.com
~9K/mo · 300/dayFree; paid removes daily cap
● Free
Required or fallback domain used
$21/mo · Pro+ only
$251/yr · free on Enterprise
Volume-based, not contact-based — distinctive in field. Dedicated IP gated at Pro. Logo removal +$12/mo on Starter.
Constant Contact
Marketing-first
● Pre-warmed
Shared CC infra
60-day trial onlyLite from $12/mo · 500 contacts
● Free
DNS records only
Not offeredNo clear IP path
No permanent free tier — forces paid from day 61. Limited deliverability tooling. No upmarket infrastructure ladder.
Klaviyo
Ecommerce-first
● Pre-warmed
Shared Klaviyo / SendGrid infra
500/mo · 250 contactsFree; paid unlimited sends
● Free
DNS records only
Enterprise onlyNot standard self-serve
Profile-based billing since Feb 2025 — all contacts billed, engaged or not. Soft overages auto-upgrade plan. No annual discount.
Omnisend
Ecommerce-first
● Pre-warmed
Shared Omnisend infra
500/mo · 250 contactsPaid from $16/mo · 6K sends
● Free
DNS records only
Not offeredNot publicly available
Shopify / Woo-native — ecommerce-only audience. SMS bundled. Contact + volume gates run in parallel.
HubSpot
CRM-first
● Pre-warmed
Shared HubSpot infra
2,000/moFree, branded · Starter $20/mo
● Free
DNS records only
BundledAfter $3–7K onboarding fee
No workflows on Starter — forces $890+/mo Professional. Mandatory onboarding ($3–7K) — largest in industry.
ActiveCampaign
CRM-first
● Pre-warmed
Shared AC infra
14-day trialStarter $19/mo · 1K contacts
● Free
DNS records only
AvailableNot prominently priced
Full automation on ALL paid tiers — explicit anti-HubSpot position. No onboarding fees · free migration. Dedicated IP not pushed at SMB.
SendGrid
Infrastructure (Twilio)
● Pre-warmed
Shared IP pools on Essentials
100/day · 60-day trialEssentials $19.95/mo · 50K/mo
● Free
CNAME domain auth
$30/mo · included on Pro ($89.95+)
+$30 each additional IP
Dedicated IP is the primary upsell — gated at Pro. Essentials: no IP, no sub-users. Free plan removed in 2025.
Mailgun
Infrastructure (Sinch)
● Pre-warmed
Shared pools on Basic/free
100/day · ~3K/mo freeFoundation $35/mo · 50K
● Free
1 domain free · 1K on Foundation+
$59/mo · included on Scale ($90/mo)
Highest in field
Pure infra play — no marketing tools. Pay-as-you-go doubled to $2/1K in Dec 2025. Overages $1.10–$1.80/1K.
Amazon SES
Infrastructure (AWS)
○ None
Verification required day one
Sandbox until approved$0.10/1K after — cheapest in field
● Free
Required from day one
Self-managedNo IP upsell · Elastic IPs via console
Pure infrastructure — no marketing layer. Sandbox approval required before live sending. Reputation, bounces, suppression all DIY.
§ 04 How the industry charges

The five-step monetization ladder.

Every major ESP, regardless of category, moves customers along the same path. The accent step is the primary infrastructure upsell — the gate where the most defensible recurring revenue is captured.

Step 01

Free / shared onboarding

Pre-warmed shared domain. Immediate sending. Daily or monthly cap enforced.

$0 · table stakes
Step 02

Custom domain auth

DKIM / SPF setup. Universally free across every major competitor. A retention tool, not a revenue lever.

$0 · universally free
Step 03

Volume & feature unlock

Monthly cap removal, automation, segmentation, A/B, branding removal. First real dollars.

$9–$20 / mo entry
Step 04 Gate

Dedicated IP

The primary infrastructure upsell across the field. Reputation isolation. Warmup required.

$21–$59 / mo · primary upsell
Step 05

Enterprise / managed

Dedicated AM, SLA, custom onboarding. HubSpot's $3–7K mandatory onboarding sits here.

$3K–$10K+ setup
§ 05 What it means

Six strategic findings.

Read these as the operating implications for product, packaging, and pricing decisions — not as observations.

i.

Custom domain auth is not a revenue lever.

Every competitor in this field offers DKIM, SPF, and custom domain setup at zero cost. It is table-stakes onboarding. Charging for it would be a market anomaly and a conversion killer.

ii.

The dedicated IP is the industry's real infrastructure upsell.

SendGrid ($30), Mailgun ($59), and Brevo ($21) all gate reputation isolation behind a paid IP. It is the clearest, most defensible monetization point in the stack — customers understand exactly why they need it.

iii.

Free tiers are being gutted across 2025–2026.

Mailchimp halved limits twice in 2026. SendGrid removed its free plan entirely in 2025. Shared free infrastructure is being rationed or paywalled to accelerate upgrade pressure across the industry.

iv.

HubSpot is the outlier on mandatory onboarding.

$3,000–$7,000 mandatory onboarding fees at Professional and Enterprise are unique to HubSpot in this set. No other platform charges for setup access — their primary mid-market lever alongside seat-based pricing.

v.

Volume gates trigger faster than users expect.

Free tiers cap at 100–500 emails/day. Any campaign approaching meaningful voter or audience contact will hit these limits within days of ramp. The upgrade trigger is baked into the architecture by design.

vi.

Ecommerce-first platforms aren't built for campaign cadence.

Klaviyo and Omnisend are Shopify-native. Profile-based, engagement-driven billing is designed for e-commerce journeys — not the burst-send, event-driven cadence of political campaigns. A genuine market gap.

§ 06 Where Campaign Nucleus lands

The recommended path: two tracks, one ladder.

Built to map directly to the patterns above. Two onboarding tracks at signup, each on its own isolated IP pool so neither audience can affect the other's deliverability reputation. Same 25K/mo allowance, same 10K profile limit, same upgrade ladder.

Track A · in-house domain

@nucleus.com — zero setup, send today.

For clients who want to start sending immediately. Pre-warmed shared pool, no DNS, no friction. Full 25K available from day one with no daily cap.

IP pool
2–3 IPs, isolated from Track B
Daily cap
None — send the full allowance any day
Setup
None
Reputation
Pool rep builds as sender volume grows
Track B · custom domain

@theirdomain.com — 30-day warmup ramp.

For clients sending from their own domain. DNS auth required. A daily ceiling rises across 30 days to protect domain reputation — designed so a sender who hits the ceiling each day still reaches the full 25K by end of month one.

IP pool
2–3 IPs, isolated from Track A
Daily cap
Rises 200 → 1,800 across month 1
Setup
DKIM / SPF / DMARC records
Reputation
Per-sender domain warmup enforced

Track B daily ceiling — 30-day warmup

Max reachable ≈ 31.7K · covers the 25K cap
Day 1–3
200/day · max 600
Day 4–7
400/day · max 1,600
Day 8–14
700/day · max 4,900
Day 15–21
1,200/day · max 8,400
Day 22–30
1,800/day · max 16,200
Max reachable across month 1 ≈ 31,700 emails — comfortably above the 25K cap

When a sender hits the limit.

Soft prompt rather than hard block. Both tracks converge on the same upgrade gate — and from there, on the existing pricing ladder.

Step 01
Soft prompt, not hard block.

Emails or profiles cap reached. Sends queue for 48 hours; sender sees two clear options side by side instead of an error wall.

No revenue event — yet
Step 02 · A
Buy more, stay on Basic.

+25K emails ≈ $15. +50K ≈ $31. +5K profiles ≈ $15. +15K profiles ≈ $45. Same IP pool, no infrastructure change.

Tier · Basic add-on
Step 02 · B
Upgrade plan.

Core at $500/mo unlocks 100K emails + profiles, A/B testing, App Store, and Shared Inbox. Enterprise is the path to dedicated IPs and custom reporting.

Tier · Core $500 → Enterprise

Two tracks at signup, two options at the upgrade gate, one pricing ladder. Conversion pressure at every stage — no friction for early users.

View the full onboarding framework — diagram Fig. 01 · v4 · 7 steps
Fig. 01 · Campaign Nucleus onboarding framework v4 Two-track signup → upgrade paths
Campaign Nucleus onboarding framework v4 New signup Automated onboarding triggered Track A Track B Track A — in-house domain @nucleus.com shared pool · no setup needed Track B — custom domain @theirdomain.com · DNS setup required IP Pool A (2–3 IPs) Exclusively for Track A senders Reputation isolated from Track B Pool rep builds as sender volume grows IP Pool B (2–3 IPs) Exclusively for Track B senders Reputation isolated from Track A Per-sender domain warmup enforced Track A limits Emails: 25K/mo · no daily cap Profiles: 10K contacts Send full 25K whenever they want Track B limits Emails: 25K/mo · daily ceiling rises Profiles: 10K contacts Full 25K reachable within month 1 Sending begins immediately Full 25K available from day 1 Bounce rate monitored per sender Bad actors auto-paused to protect pool Daily ceiling — rises over 30 days Both tracks share 25K/mo allowance Day 1–3 200/day · max 600 Day 4–7 400/day · max 1,600 Day 8–14 700/day · max 4,900 Day 15–21 1,200/day · max 8,400 Day 22–30 1,800/day · max 16,200 Max reachable ~31.7K (covers 25K) Month 2+ → 25K/mo, no daily cap Upgrade prompt — soft overlay, not hard block Emails OR profiles cap hit → sends queue 48h · CTA shows two options side by side Option A — buy more, stay on Basic +25K emails → ~$15 · total 50K/mo +50K emails → ~$31 · total 75K/mo +5K profiles → ~$15 · total 15K +15K profiles → ~$45 · total 25K Same IP pool · no infrastructure change Option B — upgrade plan Core: $500/mo · 100K emails + profiles Unlocks A/B, App Store, Shared Inbox Enterprise: dedicated IPs + custom reports Moves off shared pool entirely Dedicated client services rep Bounce monitoring >5% hard bounce → sender auto-paused Spam complaint cap >0.1% complaint rate → throttle + alert sender Unsubscribe hygiene Auto-suppress · counts against profile limit Track A (in-house) Track B (custom domain) Trigger / decision Upgrade paths