Gmail has a quick solution to that.It will automatically delete all of the spam messages in your Spam folder every thirty days.
Here are the simple steps to follow in order to delete the spams automatically from your email account.
1.Open your Gmail Settings by clicking on the Gear button.
2.Select Filters tab from it.Now click on Create a New Filter.
3.Now a window will pop-up, look for the Has the Words field in this window and type “in:spam” without quotes.
Leave all other fields empty and click Create Filter with this Search and select OK to proceed to next step.
4.Confirm your action by clicking “OK”
5.Check mark the box Delete it and Also Apply filter to next to Create Filter and click on Create Filter.
6.Now you will see a message Your Filter was Created.
That's it! Now all your spam messages will be automatically delete and there will be no message in your Spam folder anymore. Make it Simple