Mail problem - crashing

I have a 2009 bmp and have been using yosemite with no problems.

Yesterday i tried sending a video file via mail and its stuck in my outbox. I cannot delete it and when i open mail, my computer hangs and forces me to quit mail after stalling telling me there is no application memory left.

Anyone have any ideas on a remedy? Thanks

 

30 GB left out of 160

 

Should i try to repair permissions or is there a step i can take to see if that will fix the issue? Thanks!