Junk mail filter for iPhone via imap

I have: Mac Book Pro running OS X 10.10.2 iPhone 6 Plus running iOS 8.1.3

On my computer I run Mail, which checks the email every 1 min. On my iPhone it runs every 15 mins. So most of the time, my computer receives the email first and filters the message so my phone never gets the junk mail. However when my computer is sleeping my iphone normally gets the email first and does not perform the filter for the junk mail.

Options: 1) Force the computer not to sleep 2) Write a script to run while sleeping asking mail query the server (I'm not sure how hard this would be) 3) Ask here and see if someone has a better idea.

Thanks