From what I know, K2 does not support this feature. However, you can develop  your own custom solution to achieve this. Here is what I am thinking:

1. If you are using Exchange, you can use the Exchange Mailbox Service Broker from Market, and create SmartObject to read your Exchange mailbox

2. Write a C# solution, and use K2 API to call the Exchange SmartObject to read the mailbox. Once you found a mail that contains a specific keyword, use the K2 API again to call the SmartObject you want to create the new item

3. Set a schedule to execute that solution on a regular interval

Alternatively, if you know how to do it, you can also write your own code to read your mailbox if you do not want to use any SmartObjects to do that.

Is there any way to achieve this without custom coding?