RestrictExtRecips for Outlook

Purpose

You can restrict the number of recipients per message in your Exchange organization, but there is no built-in way to restrict how many external recipients a group of users can send to.

If you run the classic desktop Outlook for Windows, the RestrictExtRecips add-in will solve this problem.

Suppose an Exchange administrator has created a distribution list named "RestrictExtRecips_2". The number 2 after the underscore means that each member of this list who has the RestrictExtRecips add-in installed cannot set more than 2 external recipients per message.

If a user adds 3 or more external addresses to the "To:" or "CC:" field, the message will not be sent and Outlook will display a warning pop-up window.

The application is a COM add-in compatible only with classic desktop Outlook for Windows. It does not support the new Outlook for Windows.

Current version: 1.0.0.3

Installation

1. As an Exchange Online admin, log into the Exchange Admin Center. Create a distribution list named RestrictExtRecips_2. In the Notes field, enter the prefix "Non-restricted:" and the comma-delimited string of internal domains. Example: Non-restricted: @contoso.com, @contoso.onmicrosoft.com.
   Make sure you are a member of this list.
   
2. On a client workstation where Outlook is installed, download the RestrictExtRecips-Demo.zip file and extract all files to the C:\Program Files\IvaSoft\RestrictExtRecips folder. Exit Outlook if it is running, then run RestrictExtRecips-Demo.msi and follow the instructions.
3. Start Outlook and click File > Options > Add-ins. Select "COM add-ins" in the Manage: list box (at the bottom of the page) and click the Go button. Make sure that RestrictExtRecips is in the list.
   

Testing

1. Open Outlook and create a new message. Insert three external addresses in the "To:" field. Populate the Subject: field. Click the Send button. A warning message will appear.
   
2. Note that you can place any number of external recipients into the "BCC:" field.

Uninstallation

You can uninstall the add-in via Settings > Apps (called "Installed Apps" in Windows 11 and "Apps & features" in Windows 10).

Demo Version Notes

Using the demo, you have a predefined limit of 2 external recipients. In the full version, you can set any number from 0 (no external recipients allowed) to 500.

FAQ

Q. Will it help us be more GDPR compliant?
A. Yes. Sharing email addresses with other recipients is a breach of GDPR regulations—see this article: 5 Ways Your Emails Could Breach GDPR. With RestrictExtRecips, you can force users to use "BCC:" instead of "To:" and "CC:".

Q. How can I define the number of external recipients?
A. This number is defined by the name of the distribution list.

• To allow 5 external recipients, name the list "RestrictExtRecips_5".
• To allow 12 external recipients, name the list "RestrictExtRecips_12".
• To disable external recipients completely, name the list "RestrictExtRecips_0".

Q. What happens if the mailbox is a member of several "RestrictExtRecips_XXX" distribution lists?
A. The lowest number takes priority. So if jdoe@contoso.com is a member of both "RestrictExtRecips_2" and "RestrictExtRecips_5", the allowed number of external recipients is 2.

Q. May I hide the "RestrictExtRecips_XXX" distribution list from address lists?

A. No. Hidden distribution lists are invisible to the add-in, which will prevent it from working correctly.

Pricing and Licensing

License type

Price per unit

Single license

$35.00

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Site license

$1,500.00

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Enterprise license (including the source code)

$4,500.00

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A Site license covers a single organization at one physical location, with unlimited installs
An Enterprise license covers all computers across a single organization worldwide, including all branches and remote users.