Updated May 5, 2026: We have updated the timeline. Thank you for your patience. 

[Introduction]

We’re adding a new Exchange Online admin policy that gives admins more control over the default Mail Compose and Reply setting that determines whether commas are used as recipient separators.

This message is associated with Microsoft 365 Roadmap ID 557676.

[When this will happen]

• General availability (Worldwide): Rollout will begin in early April 2026 and complete by mid-May 2026 (previously mid‑April).

[How this will affect your organization]

Who is affected

• Exchange Online administrators in New Outlook for Windows and Outlook for Web
• All users composing or replying to email in Outlook where no per‑user override is configured

What will happen

• A new admin policy will be available to set the tenant‑wide default for “Use commas as recipient separators.”
• Admins can choose whether the default is on or off for all users.
• Users may still change this setting in their Outlook client unless an admin enforces a policy that locks it: 

  

• This update is especially useful for organizations whose contacts commonly use “Last name, First name” formats.
• No changes will occur automatically—tenants will retain existing behavior unless an admin modifies the policy.

[What you can do to prepare]

No action is required. If desired, you may configure the new admin policy after rollout if you want to establish a consistent default. You can set this value via Powershell with the command “Set-Organization Config -RecipientDelimeters <Boolean>.”

You may also consider the following actions: 

• Review your organization’s preferred recipient formatting conventions.
• Update internal documentation if your helpdesk or user‑training materials reference this setting.

[Compliance considerations]

No compliance considerations identified. Review as appropriate for your organization.