Importing email content as Sitefinity content can be easily achieved - you'll need to create a new publishing point. This can be done by going to Administration -> Feeds & Notifications, and clicking on Create a feed. From the Content to include settings you will configure the content to be imported via a pop3inbound pipe, by selecting Email as an option.
Once you've configured the content to include, you can go to Publish as... and configure the incoming content to be pulled as Sitefinity content -> blog post.
Concerning the from email notification, this forum thread
contains a detailed discussion and several solutions on the topic, I believe you might find it useful.
What remains is your last request about assigning a category to the item with the email. It is possible to configure the pipe mappings when setting up the Content to include and Publish as... , however the email has a limited number of fields that you can choose among to dedicate for specific field of the newly created Sitefinity content item. Please take a look at the attached screenshots for a better idea on what I'm talking about. For more information on how the opublishing system in Sitefinity works, and guidance on creating custom pipes, you can also browse this KB article
If you have any additional questions, please let us know, we'll be glad to help.
All the best,
the Telerik team
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