(Updated) Microsoft Outlook for iOS/Android: Large audience warnings for users

Microsoft Outlook for iOS/Android will soon warn users when emailing a large number of recipients, with the default threshold set at 25 people. The rollout starts in early May 2025 and completes by early July 2025. Admins can customize the large audience size. No admin action is required.

Updated July 1, 2025: We have updated the timeline below. Thank you for your patience.

Coming soon for Microsoft Outlook for iOS/Android: Users will receive a warning when they are about to send an email to a large number of recipients, which can help them make the correct decision about wording, tone, and content.

[When this will happen:]

General Availability (Worldwide, GCC, GCC High): We will begin rolling out early May 2025 (previously mid-April) and expect to complete by early July 2025 (previously early June).

[How this will affect your organization:]

After this rollout, users with MailTips support can opt in to receive a warning when they are about to email a large number of recipients. The default large audience size is 25 people. Learn how admins can define a custom large audience threshold for their organization: Configure the large audience size for your organization in Exchange Online | Microsoft Learn

When composing an email to a large audience, users will see an info bar above the address line and can tap the info bar to learn more:

This change will happen automatically

[What you need to do to prepare:]

This rollout will happen automatically by the specified dates with no admin action required before or after the rollout. You may want to notify your users about this change and update any relevant documentation. You may also want to modify the default large audience size (25 people) to meet the needs of your organization.

Learn more: MailTips in Exchange Online | Microsoft Learn