I'm not sure what you mean by an add-in for external out of office messages.
If you are able to use the Out of Office Assistant to send messages to
internal recipients but not internet recipients, it's probably because
automatic replies to the internet are disabled on the Exchange server (this
is the default for Exchange 5.5 and later). You'd have to ask your server
administrator to change this.
--
Jocelyn Fiorello
MVP - Outlook
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