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On the filters summary page, in our March 2015 release we added two new feature to the actions menu - ": Use in email search" and "search and Use in SMS search" - . These new features allow you to quickly search recipients using that the selected filter..
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Testing a filter
With Mailup 8.8 you can now Also new in the March 2015 release is a way for you to easily test a filter as you create it or edit it. You can do so by performing a real-time email or SMS search that returns the number of subscribers that match the filter (great feature improving your productivity improvement 
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From the example below we tested an activity filter while working on its condition and it returned 2 subscribers.
When filters are used
Filters are used for many different purposes in your MailUp admin console.
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All in all, filters are one of the most powerful feature in MailUp, and can allow you to run sophisticated marketing campaigns.
Filters and the Marketing+ package
Your MailUp account comes with a few, default filters. In order to be able to add and edit multiple filters, you will need to add the Marketing+ package to your account.