Enabling the External Recipient Mailtip in Exchange Online

How to enable the External Recipient mailtip in Exchange Online.

The External Recipient mailtip is not enabled by default, but is useful for warning users when they are about to send an email to an external user.

The External Recipient MailTip in Exchange Online offers several benefits:

Prevents Unintended Information Disclosure: It alerts users when they are about to send an email to recipients outside their organization. This helps prevent accidental sharing of sensitive or confidential information

Enhances Security Awareness: By notifying users about external recipients, it raises awareness about potential phishing or hacking attempts, where someone might be pretending to be an internal contact

Improves Communication Quality: Knowing that an email will be sent outside the organization encourages users to review the content, tone, and wording of their messages, ensuring they are appropriate for external audiences

Consistency Across Clients: The MailTip feature works across various email clients, including Outlook on the web, desktop

Mailtips have been around since Exchange 2010, however they haven’t changed much since then. Whilst rather limited in terms of functionality and customisation, the nice thing about them is that they apply to across email clients, Outlook on desktop, OWA, and Outlook mobile. Other third party plugins typically only work on Outlook desktop, so they are still a useful feature to have.

For example the external recipient mailtip can be seen as below:

Outlook (classic)

Outlook (new) – also the same as OWA.

Outlook (mobile)

The default mailtip configuration can be seen in Exchange Online as follows:

Get-OrganizationConfig | fl Mailtips*
MailTipsAllTipsEnabled : True
MailTipsExternalRecipientsTipsEnabled : False
MailTipsGroupMetricsEnabled : True
MailTipsLargeAudienceThreshold : 25
MailTipsMailboxSourcedTipsEnabled : True

According to https://docs.microsoft.com/en-us/powershell/module/exchange/organization/set-organizationconfig?view=exchange-ps, these settings do the following:

• The MailTipsAllTipsEnabled parameter specifies whether MailTips are enabled (this just enables or disables mailtips as a feature, and you can then enable or disable individual mailtips using the other options ).
• The MailTipsExternalRecipientsTipsEnabled parameter specifies whether MailTips for external recipients are enabled.
• The MailTipsGroupMetricsEnabled parameter specifies whether MailTips that rely on group metrics data are enabled.
• The MailTipsLargeAudienceThreshold parameter specifies what a large audience is. The default value is 25.
• The MailTipsMailboxSourcedTipsEnabled parameter specifies whether MailTips that rely on mailbox data (out-of-office or full mailbox) are enabled.

So, mailtips are enabled by default, but the external recipients mailtip is disable by default. To enable it, just run the following command:

Set-OrganizationConfig -MailTipsExternalRecipientsTipsEnabled:$True

Note that this will apply to all users on any version of Outlook, including OWA and mobile.

This is also a great resource for some more info: https://blogs.technet.microsoft.com/ferris/2010/03/30/howto-configure-mailtips-in-exchange-server-2010-here/