Campaign Monitor, Customer.io, and Elastic Email all send marketing email, but they serve different buyers. Campaign Monitor is a traditional drag-and-drop…
Freemium (pay-as-you-go credits plus tiered monthly subscriptions) · From Free (paid Email API plans from $19/month; Email Marketing plans from $29/month)
Best for: Developers and budget-conscious teams who want combined transactional API and SMTP sending plus basic marketing email in one account.
At a Glance
Campaign Monitor
Customer.io
Elastic Email
Primary category
Email Marketing
Email Marketing
Email Marketing
Rating
Not documented
Not documented
Not documented
Pricing model
Subscription (tiered by subscriber count)
Subscription (usage-based)
Freemium (pay-as-you-go credits plus tiered monthly subscriptions)
Starting price
From about $13/month (Lite plan)
$100/month
Free (paid Email API plans from $19/month; Email Marketing plans from $29/month)
Free plan
Yes
Not documented
Yes
Free trial
Yes
Yes
Not documented
Platforms
Web
Web
Web
Team collaboration
Not documented
Not documented
Not documented
AI features
Yes
Yes
Yes
Public API
Yes
Yes
Yes
Standout Differences
Event-based versus list-based segmentation
Customer.io segments audiences using real-time behavioral and event data, while Campaign Monitor's segmentation is built around more traditional audience lists.
Customer.io, Campaign Monitor
Elastic Email combines transactional and marketing sending
Elastic Email offers both a transactional email API and SMTP relay alongside marketing tools in a single account, avoiding the need for separate vendors and reputation pools.
Elastic Email
Only Customer.io orchestrates beyond email
Customer.io's Journeys workflow builder supports email, SMS, push, and in-app messaging from one system, a broader channel mix than either Campaign Monitor or Elastic Email documents.
Customer.io
Track record versus developer-first pricing
Campaign Monitor has been operating since 2004 and offers a nonprofit discount, while Elastic Email positions itself as a lower-cost, developer-first alternative to platforms like SendGrid and Mailgun.
Campaign Monitor, Elastic Email
Very different pricing structures
Campaign Monitor and Customer.io both scale pricing with subscriber or profile counts, while Elastic Email uses pay-as-you-go credits layered with tiered monthly subscriptions.
Campaign Monitor, Customer.io, Elastic Email
Feature-by-Feature
Sending and Automation
Feature
Campaign Monitor
Customer.io
Elastic Email
Drag-and-drop email builder
Available
Not documented
Available
Marketing automation workflows
Available
Available
Available
Transactional email API or SMTP relay
Available
Not documented
Available
Targeting and Channels
Feature
Campaign Monitor
Customer.io
Elastic Email
Real-time behavioral or event-based segmentation
Limited
Available
Limited
Multi-channel messaging (SMS, push, in-app)
Unavailable
Available
Unavailable
A/B testing
Available
Available
Not documented
Pricing and Access
Feature
Campaign Monitor
Customer.io
Elastic Email
Permanent free plan
Unavailable
Unavailable
Available
Self-serve free trial
Available
Available
Available
Pricing Compared
Starting price reflects the lowest paid tier, not the full cost for every team size or usage level.
Campaign Monitor
Free Trial — $0 30-day trial
Lite — From ~$13/month monthly or annual
Essentials — From ~$31/month monthly or annual
Premier — From ~$171/month monthly or annual
Enterprise — Custom annual
Customer.io
Essentials — $100/month Monthly
Standard — Custom Monthly or annual
Premium — From ~$1,000/month Annual
Enterprise — Custom Annual contract
Elastic Email
Free — $0 monthly
Starter (Email API) — $19 monthly
Pro (Email API) — $49 monthly
Email Marketing — From $29 monthly
Pros & Cons
Campaign Monitor
Pros
Established platform with a long track record dating back to 2004
Easy-to-use drag-and-drop builder suited to non-technical marketers
Unlimited sends on Essentials and higher tiers
15% discount available for nonprofit organizations
Cons
Pricing scales with subscriber list size, which can get expensive for larger lists
The entry Lite plan caps monthly sends rather than offering unlimited sending
Ownership changes (CM Group to Marigold, and the 2025 sale of the enterprise business to Zeta Global) have added brand confusion
Fewer advanced e-commerce automation features than commerce-focused competitors
Multi-channel orchestration (email, SMS, push, in-app) from one workflow builder
More affordable entry pricing than Braze or Iterable for similar behavioral capabilities
Strong API and SDK support for developer-driven data instrumentation
Cons
Pricing scales quickly with profile and email volume
Steeper learning curve than simple email marketing tools due to data-model flexibility
No permanent free plan, only a 14-day trial
Advanced tiers (Premium/Enterprise) require custom sales negotiation for pricing
Elastic Email
Pros
Combines transactional and marketing email in one account, avoiding the need for separate vendors and reputation pools.
Pricing is generally lower than comparable developer-focused competitors like SendGrid, Mailgun, and Postmark.
Free tier and self-serve signup make it easy to test integrations before committing to a paid plan.
Supports both a full REST API and a standard SMTP relay, easing migration from self-hosted mail servers.
Cons
Deliverability reputation can be inconsistent on shared IP pools compared to specialist transactional providers like Postmark.
Marketing automation and design tools are less sophisticated than dedicated marketing platforms like Mailchimp or Klaviyo.
Customer support response times can lag on lower-tier plans without a paid support add-on.
Documentation and UI polish trail some larger, venture-backed competitors.
Use Cases
Choose Campaign Monitor: Marketing teams who want an easy drag-and-drop builder and an established campaign platform without much technical setup.
Choose Customer.io: Product and growth teams that need event-based behavioral segmentation and multi-channel messaging across email, SMS, push, and in-app.
Choose Elastic Email: Developers and budget-conscious teams who want combined transactional API and SMTP sending plus basic marketing email in one account.
Campaign Monitor
Small Business Newsletters — Small businesses use Campaign Monitor's templates and segmentation to run regular email newsletters and promotions.
Agency Client Management — Marketing agencies use Campaign Monitor to manage email campaigns for multiple clients from one account.
Nonprofit Donor Communications — Nonprofits use Campaign Monitor's discounted plans to run donor newsletters and fundraising campaigns.
Customer.io
Lifecycle and retention marketing — Automated email and multi-channel journeys to onboard, engage and retain users based on behavior.
Behavioral triggers — Cart abandonment, feature-adoption nudges and onboarding sequences triggered by product events.
Multi-channel campaign orchestration — Coordinated email, SMS, push and in-app campaigns from a single workflow builder.
Elastic Email
Transactional Email for SaaS Products — Developers integrate the API or SMTP relay to send account notifications, password resets, and receipts reliably at scale.
Combined Transactional and Marketing Email — Businesses that need both system emails and periodic newsletters manage both from a single account and reputation pool.
White-Label Email Delivery for Agencies — Agencies use sub-accounts and reseller features to manage email sending on behalf of multiple clients under one master account.
Frequently Asked Questions
Is Customer.io the same kind of tool as Campaign Monitor?
Not exactly. Campaign Monitor is a traditional drag-and-drop email marketing platform, while Customer.io is a behavioral engagement platform built around event data and multi-channel messaging across email, SMS, push, and in-app.
Which is cheapest to start with?
Elastic Email has a genuinely free tier. Campaign Monitor starts at roughly $13 per month, and Customer.io starts at $100 per month, though pricing on all three scales with volume or list size.
Which supports SMS and push notifications in addition to email?
Customer.io, through its multi-channel Journeys workflow builder; Campaign Monitor and Elastic Email are documented as email-focused platforms.
Can Elastic Email be used for both transactional and marketing email?
Yes, Elastic Email combines a transactional email API and SMTP relay with marketing email tools in a single account.
Which platform has the longest track record?
Campaign Monitor, founded in 2004, predates both Customer.io (2012) and Elastic Email (2010).
Which is best for event-driven, behavior-triggered messaging?
Customer.io, which is built specifically around real-time behavioral data and event-based segmentation rather than static contact lists.