Seems you are not alone with this problem... this may help.
Problem: Just updated my Galaxy S5 to the new software, as directed. All is fine except for email. I keep getting “Unfortunately Email has stopped.” What can I do to fix this ?
Troubleshooting:. We know for a fact that not all system updates can go perfectly as intended. Some instances of system updates can even do more harm than good, not because they are designed to do exactly that, but simply because of some complications when incompatible firmware versions or damaged apps get intertwined with the system update files. If this problem happened immediately after the update, your first troubleshooting step is to try to identify if this involves only the email app you are using. We recommend that you clear the email app’s cache and data, then reconfigure your email to the said app afterwards.
Just follow these steps on how to clear an app’s cache and data:
• Go to Home screen.
• Open the Apps list.
• Go to Settings.
• Go to Applications.
• Touch Application manager.
• Look for the app in question.
• Tap Clear data.
• Tap OK.
• Tap Clear cache.
If that will not work, perform a factory reset and reconfigure your email to see if that will make any difference.
Read more at
http://thedroidguy.com/2015/02/samsung-galaxy-s5-problems-glitches-questions-errors-solutions-part-25-102793#YcPJOpy3iqAVRjPQ.99