You didn't specify which app you're using for email - if you're referring to Gmail, then at the bottom of main screen, select the 2nd icon from the right (looks like a pair of cards), then choose Sent - voila!
I don't use the stock email application so I can't offer a suggestion there.
Sent from my rooted, debloated, deodexed Sinclair ZX-80 running CM -0.001 using Tapatalk 2