Mail Contacts

Manage external mail contacts in Exchange Online. Mail contacts represent external recipients who appear in the Global Address List (GAL), making it easy for users to send email to frequent external contacts.

Note: Mail contacts have external email addresses and appear in the GAL but cannot sign in. Mail users have external addresses but CAN sign in to Microsoft 365 (with limited access).

Mail Contact List

Common Use Cases

Partner Contacts

Add key contacts from partner companies to GAL so employees can easily find and email them without remembering addresses.

Vendor Contacts

Maintain contacts for vendors and suppliers. Include company and department info for context.

Consultant Access

Add external consultants to address book. They appear in GAL but don’t have Microsoft 365 accounts.

Distribution List Members

Add external recipients to internal distribution lists. Mail contact must exist before adding to group.

Creating a Mail Contact

Basic Information

• Display Name — Full name shown in address book
• Alias — Short name (used for internal routing)
• External Email — The actual email address for delivery

Contact Details

• First and Last Name
• Title and Department
• Company Name
• Phone Numbers
• Street Address

Organization

• Manager (optional)
• Direct Reports (optional)
• Custom Attributes

Mail Contact Properties

Email Addresses

Mail contacts have proxy addresses that route to the external email:

• Primary SMTP — Default reply address (usually external)
• Additional addresses — Aliases for the contact
• X500 — Legacy Exchange address for migrations

Mail Flow Settings

• Message delivery restrictions (who can send)
• Accept messages from specific senders only
• Reject messages from specific senders
• Require authentication for senders

MailTip

Custom message shown to senders in Outlook before they send. Useful to note “External - verify before sending sensitive info”

Hiding from GAL

Hide mail contacts from the Global Address List when:

• Contact is only used for distribution list membership
• Contact is for system or automated processes
• Contact should only be accessible to specific users
• Contact is temporary and shouldn’t be searchable

Note: Hidden contacts can still receive email. Senders just can’t find them in address book.

Bulk Import

Import multiple mail contacts via CSV:

CSV Columns

Best Practices

• Use consistent naming — Format: “Last, First (Company)” so contacts sort properly in GAL.
• Include company information — Populate company and department fields for context in address book.
• Review regularly — Remove contacts when business relationship ends to keep GAL clean.
• Use MailTips — Remind senders that recipient is external before they send sensitive data.

API Reference

GET /api/exchange/mail-contacts List all mail contacts

POST /api/exchange/mail-contacts Create mail contact

PUT /api/exchange/mail-contacts/:id Update mail contact

DELETE /api/exchange/mail-contacts/:id Delete mail contact

POST /api/exchange/mail-contacts/import Bulk import from CSV