"The following recipient is outside the organization" MailTip is displayed even though the recipient is a person in your Office 365 organization

When you create an email message in Microsoft Outlook 2010 or a later version in a Microsoft Office 365 environment, the following MailTip message is displayed even though the recipient is a person in your organization:

This issue occurs if the following conditions are true:

• The External Recipients MailTip is enabled.
• The domain that the recipient belongs to isn't associated with the organization in Exchange Online.

To fix this issue, use one of the following methods.

Method 1: Add the domain to Office 365 and verify it

If a domain isn't associated with the organization in question, it's considered an external domain. This association is set up by adding a new accepted domain in Exchange Online. To add a new accepted domain to the list of available domains in Exchange Online, the domain must be added as a verified domain in the Office 365 portal.

For more information about how to add and verify a domain in Office 365, go to one of the following Microsoft websites:

• Office 365: Internet domains
• Office 365 pre-upgrade:
  • Office 365 for enterprises: Add your domain to Office 365
  • Office 365 for small businesses:�Add your domain to Office 365

Method 2: Disable the External Recipients MailTip

To disable the External Recipients MailTip, follow these steps:

1. Connect to Exchange Online by using�remote PowerShell. For more information about how do to this, go to the following Microsoft website:
   Connect to Exchange Online Using Remote PowerShell
2. Run the following Windows PowerShell cmdlet:

   Set-OrganizationConfig -MailTipsExternalRecipientsTipsEnabled $false

MailTips are informative messages that are displayed to users when they compose an email message. MailTips are available only in Outlook Web App and in Outlook 2010 and later versions. As a user creates an email message, Outlook checks whether any MailTips apply to the message, based on configuration information that's retrieved from Exchange Online. If a MailTip does apply, it's displayed above the address field of the email message. For example, a MailTip is displayed to let you know that the person who you are composing a message to is out of office.

For more information about MailTips, go to the following Microsoft websites:

• Turn MailTips on or off
• MailTips

Still need help? Go to the Office 365 Community website.