Compare CMRelay to Other SMTP Relay Services

Not all SMTP relay services are built for the same job.

Services such as SMTP2GO, SendGrid, Mailgun, and Amazon SES are powerful email delivery platforms. But most were designed primarily for applications, websites, transactional email, and high-volume messaging.

CMRelay is different. It is purpose-built for copiers, scanners, multifunction printers, UPS systems, PBXs, monitoring systems, and other legacy SMTP devices that need to send email through modern Microsoft 365 or Google environments.

CMRelay focuses on three things that matter especially for legacy devices: security, simple deployment, and compatibility with equipment that was never designed for modern authentication.

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SMTP Relay Service Comparison

The table below compares CMRelay with several popular SMTP relay and transactional email providers.

Feature	CMRelay	SMTP2GO	SendGrid	Mailgun	Amazon SES
SMTP Relay	✅	✅	✅	✅	✅
Purpose-built for copiers, scanners & legacy SMTP devices	⭐ Yes	⚠️ General-purpose	❌	❌	❌
Works with devices that do not support OAuth	✅	✅	⚠️	⚠️	⚠️
No SMTP username/password required on device	⭐ Yes	⚠️ Depends on auth method	❌	❌	❌
Works without a static public IP	⭐ Yes	⚠️ Depends on auth method	✅ With credentials	✅ With credentials	✅ With credentials
Device-specific verification	⭐ Device ID	❌ No comparable feature	❌	❌	❌
Authorized sender verification	✅	✅	✅	✅	✅
Source IP verification	✅	✅	⚠️ Available	⚠️ Available	⚠️ Requires AWS configuration
Dynamic-IP authorization without SMTP credentials	⭐ Subject Auth Code	⚠️ Different approach	❌	❌	❌
Three-layer device authorization	⭐ Yes	❌ No comparable feature found	❌	❌	❌
Microsoft 365 delegated OAuth sending	⭐ Yes	❌	❌	❌	❌
Google delegated OAuth sending	⭐ Yes	❌	❌	❌	❌
HIPAA / BAA support	⭐ Yes	⚠️ Contact vendor	❌ No BAA	✅ Qualifying plans	✅ HIPAA-eligible
MSP / multi-customer management	⭐ Yes	✅	⚠️ Available	⚠️ Available	⚠️ AWS account architecture
Save attachments to SharePoint / OneDrive	⭐ Yes	❌	❌	❌	❌
Save attachments to Google Drive	⭐ Yes	❌	❌	❌	❌
Bulk / marketing email platform	❌ Not the focus	✅	✅	✅	✅
Email API for developers	⚠️ Not the core product	✅	✅	✅	✅

Legend: ✅ Supported ⭐ CMRelay-specific advantage ⚠️ Conditional, different implementation, or plan-dependent ❌ Not available / no comparable built-in feature

General-purpose SMTP providers can often support legacy devices when those devices support the provider’s required authentication method. Product capabilities, compliance offerings, and plan availability may change. Verify current requirements directly with each provider.

CMRelay Was Built for Devices, Not Applications

Traditional SMTP relay platforms are commonly designed around applications, websites, API integrations, and transactional email.

CMRelay starts from a different question:

How do you securely connect equipment that only understands traditional SMTP to modern Microsoft 365 and Google email environments?

That includes equipment such as:

Copiers and multifunction printers
Document scanners
UPS monitoring systems
PBX and voicemail systems
Network monitoring appliances
Building management systems
Security systems
Industrial equipment
Legacy applications

Three-Layer SMTP Authorization

One of the biggest differences between CMRelay and traditional SMTP relay services is how a sending device can be authorized.

Many traditional SMTP services rely primarily on a reusable SMTP username and password or a trusted source IP address.

CMRelay can instead verify multiple attributes of each connection and message before allowing it to relay.

1. Registered Device ID

The message must originate from a device that has been registered and authorized within CMRelay.

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2. Authorized Sending Address

The From address must match an email address that has been explicitly authorized for that CMRelay account.

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3. Authorized Network or Subject Auth Code

The device can be verified using an approved public IP address or, for locations without a static IP, a CMRelay Subject Authorization Code.

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Message Authorized

This approach provides an additional layer of protection for equipment that may not support modern authentication and may not securely support storing reusable SMTP credentials.

No Static IP? No Problem.

IP-based SMTP relay works well when an office has a dedicated static public IP address.

But many small offices, branch offices, medical practices, home offices, and remote locations use Internet connections where the public IP address can change.

CMRelay’s Subject Authorization Code provides another way to verify an authorized device without requiring a permanent public IP address or traditional SMTP username and password authentication on the device.

This makes CMRelay particularly useful for devices that have limited SMTP authentication capabilities.

Modern Microsoft 365 and Google Delivery

CMRelay does more than accept SMTP from the legacy device.

Once an authorized message reaches CMRelay, it can be delivered through a connected Microsoft 365 or Google mailbox using delegated OAuth authentication.

The legacy device continues using the simple SMTP functionality it already understands while CMRelay handles the modern cloud authentication on its behalf.

Copier / Scanner
Legacy SMTP

→

CMRelay
Secure Device Relay

→

Microsoft 365 / Google
OAuth Delivery

HIPAA Support for Healthcare Organizations

Healthcare organizations often face an additional problem: keeping older copier and scanner workflows operational while meeting modern security and compliance requirements.

CMRelay offers HIPAA-supporting service options and Business Associate Agreements for qualifying customers and plans.

Combined with CMRelay’s device verification model and OAuth-based Microsoft 365 and Google delivery, this makes CMRelay especially well suited for medical practices, healthcare organizations, and MSPs supporting regulated customers.

Scan Directly to SharePoint, OneDrive, or Google Drive

CMRelay can also extend a traditional Scan-to-Email workflow into Scan-to-Cloud.

With CMRelay Cloud Connections, email attachments can be saved directly to:

Microsoft SharePoint
Microsoft OneDrive
Google Drive

This allows organizations to continue using existing scanners and copiers while adding modern cloud storage workflows without replacing the equipment.

Which SMTP Relay Is Right for You?

Choose a general-purpose provider such as SendGrid, Mailgun, or Amazon SES if your primary need is application-generated transactional email, API-based sending, bulk delivery, or developer infrastructure.

Consider SMTP2GO if you need a broad SMTP relay platform for multiple types of applications and devices, along with traditional SMTP relay and deliverability features.

Choose CMRelay when your primary challenge is securely connecting copiers, scanners, multifunction printers, UPS systems, PBXs, or other legacy SMTP devices to modern email systems.

CMRelay Is Especially Well Suited For

Organizations replacing legacy Microsoft 365 SMTP authentication
Copier and scanner Scan-to-Email
Locations without static public IP addresses
Devices that cannot securely store SMTP credentials
Microsoft 365 environments using OAuth
Google Workspace environments using OAuth
Healthcare organizations requiring HIPAA support
MSPs managing multiple customer environments
Copier dealers supporting customer Scan-to-Email
Organizations adding SharePoint, OneDrive, or Google Drive scan workflows

Give Your Legacy Devices a Modern Email Connection

Keep the copier, scanner, or SMTP device you already have while CMRelay handles secure delivery to modern email services.

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No credit card required.

MSPs and Copier Dealers

CMRelay also offers a Partner Program for MSPs and copier dealers that need to manage Scan-to-Email and SMTP relay services across multiple customers. Partner accounts include discounted reseller pricing, centralized customer management, and a limited NFR account for internal use, testing, demonstrations, and training.

Learn more about the CMRelay Partner Program →

Comparison information is provided for general informational purposes and is based on publicly available product information. Features, plan availability, compliance programs, and service capabilities may change. Verify current requirements directly with each provider before making a purchasing decision. CMRelay is not affiliated with SMTP2GO, Twilio SendGrid, Mailgun, or Amazon Web Services.