Outlook Plug-in: External Watch - Get Alert when a message is designate outside your organization.

Have you ever asked yourself how can you alert your CEO that the message s/he is about to Reply (Reply All - 28 recipients...) is about to fly out from your organization Exchange Server to another company's mail servers?

Well if you did, then here is a simple way to do so:

I have created a simple Add-in for Microsoft Outlook (2000, 2003, and 2007) for this single purpose.
Let's see how it works:

  • Your Exchange user is receiving a message that requests him to reply-all with a sensitive business data.

outlook new message arrival

outlook message header
  • S/He then clicks the reply all button.

outlook message header and reply all
(In a single recipient message, it is easy to see the problem, but what about the 28 recipient messages that your CEO almost replied to)

  • And add the information requested at the mail:

the sensitive data at the outlook message
  • S/He clicks the Send Button.

external watch plugin - main alert

As you can see, there is now a modal message that indicates that the message designated outside the company.

You can now return to the message and remove/replace the problematic recipient/s, or click the "More Details" button to find the problematic recipient/s.

external watch - more details view

It could be that you are aware that your message is designate to third party recipient/s; in this case, it is not a problem, just show the add-in that this is your intention and add to the end of your subject the phrase: "$OUTSIDE$", the add-in will not ask you anything and will just sent the message immediately.
(The "$OUTSIDE$" will be remove from the subject before sending the message)

external watch - modified subject

How to Install:
1. Download the add-in archive from Here
or visit my Google group Home
2. Extract the archive.
3. Copy the File "olkExternalWatch.dll" to your system32 folder ("C:\windows\system32\")
4. Register it using the regsvr32.exe - "Regsvr32.exe c:\windows\system32\olkExternalWatch.dll"
5. Restart your outlook.
(I've made a batch file that will do all the tasks above for you in a one click - "install.bat")

Thanks to Yuval Malachi that gave me the idea of creating the same plug-in but without the "$OUTSIDE$" thing (or as we called it - warn only mode)
you can download the Warn only mode here

A screen shot of the new version:

External Watch - Warn Only mode

How to Disable:

Outlook 2007:
Tools Menu - Trust Center - Add-ins - Com Add-ins - Go
outlook 2007 Com Add-ins manage

Unchecked the "ExtrenalWatch" check box.

Outlook 2007 Com add-ins enable/disable

Outlook 2003:
Tools Menu - Options - Other Tab - Advanced Options - Com Add-ins
Outlook 2003 Com Add-ins manage

Unchecked the "ExtrenalWatch" check box.

Outlook 2003 Com Add-ins Enable/Disable

How to uninstall:
Just unregister it using the regsvr32.exe - "Regsvr32.exe c:\windows\system32\olkExternalWatch.dll /u" and restart your outlook.

Hope you will find it useful.



  1. very nice ,
    If i want it only to warn me but without manualy paste the $OUTSIDE$
    in the message .
    Is there an option to make it a warn mode and not active block mode

  2. Hi Yuval,
    No, Currently there is no option of "warn only" mode, but this is actually a good idea and maybe i'll implement it soon.