Email due to inactivity on a form

One way to accomplish this is to create a site workflow to find the overdue items (7 and 30 days) and run it on a desired schedule (i.e. daily, weekly, monthly). Below are steps to configure this. Note that my version is Nintex Workflow 2013.

1, Create a site workflow on your site.
2. Configure the workflow.
3. Add and configure a “Calculate date” action to the workflow to find 7 days ago.

• Date = Check the “Use date when action is executed” option
• Days Value -7
• Store date in = dtTodayMinus7 (or whatever you would like to call this DateTime workflow variable)

4.  Add a “Calculate date” action to the workflow to find 30 days ago.

• Date = Check the “Use date when action is executed” option
• Days Value -30
• Store date in = dtTodayMinus30 (or whatever you would like to call this DateTime workflow variable)

5.  Add and configure a "Query list" action to find the 7 day overdue items.

• List = Your list
• Filter = Select items only when the following is true:
• DueDate is less than or equal to dtTodayMinus7
• Field = ID and store in a collection available (colProjects7)

6.  Add and configure a "For Each" action.

• Target collection = colProjects7
• Store result in = txtCurrentID7 (text workflow variable you create)
• Add and configure a "Send notification" action in the “For Each” loop to send to the name in the field.

7.  Repeat Steps 3-6 for 30 days overdue items.

8.  Publish the workflow.

9.  You could then schedule the site workflow to run on a desired interval or run it on demand.