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In the Vault, go to Tools, Administration, Vault Settings. Behaviors tab, then click Rules under Edit and Manage Categories.
Create a new rule, name it whatever you want, and select the Category.
In the rules property builder, select File Extension, Under Condition select "Is", and in Value type the extension WITHOUT the dot (.) Example a text file would be txt, not .txt. Check the box that says Apply on object creation, and hit Apply or OK. Create a new rule for each extension you want to set. Works great, it sets the category when you check the file in for the first time.
Hope this helps.
Chris Benner
Inventor Tube & Pipe, Vault Professional
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You can but you need to have a rule for each file extension, like this:
Is it though? Granted it's time consuming, but I set up these rules around 2 years ago and haven't had to touch them since... it's a one off thing that you do and then it's done, and you can add to them at any time.
It's up to you though, if you don't create the rules you won't get the automatic category assignment 
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