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ContactMonkey supports multiple distribution list and group types through two expansion methods: Graph Backend and Exchange Online Admin API. This reference guide helps you understand which lists work with each method and how to choose the right expansion approach. It is recommended that you enable both Graph and Exchange Online Admin API for maximum compatibility with all your list types. Click here for setup instructions.

Note: List Management contact lists do not require Exchange Online Admin or Graph Backend to expand recipients.

Compatibility Matrix

Supported Recipient Types Within a List

When ContactMonkey expands a distribution list, it includes members of the following Exchange recipient types:
UserMailbox, GroupMailbox, SharedMailbox, RoomMailbox, SchedulingMailbox, MailContact, and MailUser.

Members of any other recipient type are skipped during expansion and won't appear in your recipient count. 

List Type Descriptions

Static Distribution List

What they are: Traditional distribution lists with a fixed, manually managed membership.

Characteristics:

• Members added/removed manually by administrators
• Can be nested (contain other distribution lists)
• Most common list type in organizations

Best expansion method: Either (both work equally well)

Example use cases:

• Department teams (e.g., Sales, Marketing)
• Project groups
• Location-based lists (e.g., NYC Office)

Security Group

What they are: Groups primarily used for assigning permissions, but can also be used for email distribution.

Characteristics:

• Managed in Microsoft Entra (Azure AD)
• Can have mail-enabled property
• Often used for SharePoint/Teams access

Best expansion method: Either (both work equally well)

Example use cases:

• Department-wide security and communication
• Resource access groups that also need email
• Role-based groups (e.g., "Managers")

Universal Group

What they are: Groups that can contain members from any domain in a multi-domain forest.

Characteristics:

• Cross-domain functionality
• Can be mail-enabled
• Common in large, multi-domain organizations

Best expansion method: Either (both work equally well)

Example use cases:

• Global company announcements
• Cross-subsidiary teams
• International project groups

Dynamic Distribution List

What they are: Lists whose membership is automatically determined by filter rules and queries.

Characteristics:

• Membership updates automatically based on criteria
• Rules based on user attributes (department, location, title, etc.)
• Members cannot be manually added/removed

Best expansion method: Exchange Online Admin Backend only ⚠️

Example use cases:

• All employees in a specific department
• All users with a particular job title
• All users in a geographic location

Why Graph doesn't work: Microsoft Graph API does not support expanding dynamic distribution lists. This is a Microsoft limitation, not a ContactMonkey restriction.

O365 Dynamic Group

What they are: Azure AD dynamic groups with membership based on user or device properties.

Characteristics:

• Managed in Microsoft Entra (Azure AD)
• Membership rules based on attributes
• Similar to dynamic distribution lists, but cloud-native

Best expansion method: Graph Backend only ⚠️

Example use cases:

• All users with specific license assignments
• Automatically grouped by employment status
• Device-based groups (e.g., all iOS users)

O365 Group (Modern Group)

What they are: Modern collaboration groups with email, shared files, calendar, and potentially Teams/SharePoint integration.

Characteristics:

• Cloud-native Microsoft 365 groups
• Includes additional collaboration features beyond email
• Members have shared resources

Best expansion method: Graph Backend only ⚠️

Example use cases:

• Project teams with shared workspace
• Department groups with collaboration needs
• Cross-functional teams

Distribution List with Hidden Members

What they are: Distribution lists where membership is not visible to users outside the group.

Characteristics:

• Members cannot see who else is in the group (unless they're admins)
• Often used for privacy or security reasons

Best expansion method: Exchange Online Admin Backend only ⚠️

Example use cases:

• Executive communications
• Confidential project teams
• HR or legal department lists

Hidden Distribution List

What they are: Distribution lists that do not appear in the Global Address List (GAL)

Characteristics:

• Not visible in address book searches
• Can still receive email if the address is known
• Often used for internal or administrative purposes

Best expansion method: Either (both work equally well) 

Example use cases:

• Internal testing groups
• Administrative distribution lists
• Backup or archive email groups

External Recipients

With SendGrid

Click here to learn more about external sending through SendGrid.

Without SendGrid

External recipients (email addresses outside your organization) have different support depending on your setup:

Graph Backend

⚠️ Guest accounts require additional enablement by the ContactMonkey Support team.

Exchange Online Admin Backend

On-Premise Distribution Lists

• ❌ Generally not supported
• Exchange Online Admin Backend supports the following On-Premise Distribution List 
  • Dynamic Distribution Groups
• May work in hybrid configurations with limited functionality
• Most Microsoft APIs cannot reliably access on-premise resources

Contact Group

What they are: Personal contact groups created by individual users in Outlook.

Characteristics:

• Stored in user's mailbox
• Private to the user who created them
• Cannot be shared across organization

Best expansion method: Neither - click here to learn more

Migration Path

If you have on-premise distribution lists:

1. Option A: Migrate to Microsoft 365
   • Move lists to Exchange Online Admin
   • Full ContactMonkey compatibility
   • Recommended long-term solution
2. Option B: Use CSV Upload
   • Export list members from on-premise Exchange
   • Upload as CSV when sending via ContactMonkey
   • Bypasses API expansion entirely
3. Option C: Use List Management
   • Create equivalent lists in ContactMonkey
   • Manually sync membership as needed

Nested Distribution Lists

What Are Nested Lists?

Nested lists are distribution lists that contain other distribution lists as members.

Example:

"All Staff" contains:
  ├── "Sales Team" (10 members)
  ├── "Marketing Team" (8 members)
  └── "Support Team" contains:
        ├── "Tier 1 Support" (5 members)
        └── "Tier 2 Support" (3 members)

Total unique recipients: 26

Expansion Behavior

Both Graph and Exchange Online Admin Backend support nested lists:

• ContactMonkey recursively expands all nested lists
• Deduplicates recipients appearing in multiple lists
• Reports accurate unique recipient count

Performance Considerations

Nesting Level:

• 1-3 levels: Fast expansion (< 5 seconds)
• 4-7 levels: Moderate expansion (5-15 seconds)
• 8+ levels: Slower expansion (15+ seconds)

Best practice: Limit nesting to 3-4 levels for optimal performance.

Frequently Asked Questions

Q: Can I use both Graph and Exchange Online Admin for the same email?
A: No, you select one expansion method per email send. The method is chosen when you compose the email.

Q: What happens if I choose the wrong expansion method?
A: You may get an inaccurate recipient count, or the email may fail. Always run a test count to verify before sending.

Q: Can I convert a dynamic distribution list to a static one?
A: Yes, but you'll need to manually maintain membership. Work with your IT administrator to:

1. Create a new static distribution list
2. Copy current members from the dynamic list
3. Update membership manually going forward

Q: Why does Microsoft limit Graph API for dynamic lists?
A: This is a Microsoft platform limitation. Dynamic list membership is calculated on-demand based on query rules, which Graph API doesn't support. Exchange Online Admin API provides this capability through different underlying mechanisms.

Q: Can a distribution list be both hidden and dynamic?
A: Yes, the Exchange Online Admin API can expand dynamic lists and access hidden membership.

You could also choose to use CSV upload or contact your IT administrator to adjust the list configuration.

Q: How often does ContactMonkey check list membership?
A: List membership is expanded in real-time when you compose an email or run a test count. ContactMonkey doesn't cache list membership beyond a few minutes for performance optimization.