Can we change the default MailTips message for all external recipients?

We are runnng Exchange 2013.

We've enabled the MailTip to flag when an email is addressed to recipients outside the organisation using the following command:

Set-OrganizationConfig -MailTipsExternalRecipientsTipsEnabled $true

We are based in Britain and therefore would like to change the default message from: 

"The following recipient is outside your organization" to "The following recipient is outside your organisation"

i.e. the word "organisation" to UK spelling. I wonder if this is possible by either changing the culture of the message or customising the message itself?