Is it possible to create or modify items of a List by sending emails? i.e. Change status of the task etc.
You can email enable a document library and then trigger a SharePoint designer workflow to take action when an email arrives.
Note that these incoming email are processed in the context of the system account (as there is no active user). This may prevent the workflow from running for security reasons. More details and a possible workaround can be found here.
A tutorial about how to use this facility to convert emails to PDF format using a workflow can be found on my company's blog.