If you’re like me you probably have a lot of email addresses that auto-complete in Outlook because you spend a lot of your professional life in email.

As some point I bet you’ve also emailed Alan Smith at an external supplier rather than Alan Smyth in accounts because Outlook auto-complete did its thing and you didn’t notice. That is, until that split second after you clicked ‘Send’ or when Alan Smith replied with an email along the lines of “Errrr, don’t think this was meant for me”.

While Exchange Server (on-premises or Online in Office 365) provides us with many features designed to stop leakage of important business information there is a very simple way (without using DLP) that we can help users avoid the above scenario.

Our old friend MailTips.

MailTips have been around since Exchange and Outlook 2010, but some of these items are switched off by default. One of these disabled items is the “External Recipients” MailTip.

You can enable the MailTip display using the below PowerShell (you’ll need to be an Exchange Admin for this to work).

[code language=”PowerShell”]
Import-Module MSOnline

$cred = Get-Credential

$exoSession = New-PSSession -ConfigurationName Microsoft.Exchange `
-ConnectionUri "https://outlook.office365.com/powershell-liveid/" `
-Credential $cred -Authentication "Basic" -AllowRedirection

Import-PSSession $exoSession

Set-OrganizationConfig -MailTipsExternalRecipientsTipsEnabled $true


Once we’ve made this change users will begin to see warnings in their Outlook clients (both desktop and web) that look similar to the below and will hopefully be alerted if they are sending a mail to the wrong person.

Outlook on the web - External Recipient Warning

Outlook - External Recipient Warning

Happy Days! 🙂

Communication and Collaboration, Exchange, Office 365
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Join the conversation! 10 Comments

  1. Can you disable the mail tip for a specific recipient outside your organisation?

  2. can you explain this line in your solution
    -ConnectionUri “https://outlook.office365.com/powershell-liveid/” `

  3. Great article Simon. How can you test a Mailtip change before rolling it out to the entire organisation? Can we test it for a limited user group first?

  4. Can you specify which mailboxes the mailtip will work for as oppose to turning it on for the entire organization?

  5. Can you modify/edit the default External Recipients MailTip to say something else?

  6. What is the power shell command syntax to enable mail tips for oversize large email attachment. i want to see a mail tip notifying the sender the attachment is too large to send by email.

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