Enable the External Recipients MailTip
We have recently enabled the External Recipients MailTip – primarily to reduce the risk of users sending confidential messages to users outside of the organisation and then asking to have them recalled, which isn’t possible.
This is easy to do using the following PowerShell command:
Set-OrganizationConfig -MailTipsExternalRecipientsTipsEnabled $true
Now, when users begin composing an email, they are advised if the recipient is outside the organisation.
Note: this cannot be enabled using the EMC