I had a particular problem with my e-mails. I belong to multiple mailing lists at work, so when someone sends an e-mail to all of them, I get several copies, like the following picture illustrates

There was no way of fixing it with rules, as they are n different e-mails, not the same one.

After a little search, I couldn’t find anything to fix this, so I programmed a little add-in to deal with it (you can download both the binaries and the source at the end).

It works like this:

• You provide a list of addresses by priority
• If an e-mail is from one of those addresses (evaluated in order), and one recipient is in the list above the current one, the mail is deleted (as you have already received it with that previous address)

Easy! So easy, I may be missing something, if so, please let me know.

To install it, download the binaries and double-click the MailingListFilter.vsto file (you need to have the Visual Studio Tools for Office installed), if that doesn’t work, you can go to Tools –> Trust Center –> Add-ins –> Go…, there you can add it manually. Perhaps I’ll add an installer later.

To configure it, go to Tools –> Mailing List Filter…

Remember to specify them in priority order (it’s a good idea to add your personal address first).

The code is based on this example.
You are free to download and modify the code, if you publish a modification, a link here would be nice.

Known Issues

Despite the documentation claiming the event I use (NewMailEx) is guaranteed to fire, I found that this is not always true. There are certain cases of race conditions with Outlook rules, and if you have one set to move mails to subfolders, the event may not fire. So in order for this add in to work, you shouldn’t have rules to move the eligible mails to subfolders; it’s kind of annoying, so I’ll post a fix if I ever find one.

Downloads