Same happened to me because I was messing with my apps in applications manager and accidentally must have got rid of that, anyway... you can do what I did until you get a proper solution and please when you do let me know because I dont know how to upload questions here anyway, the quickest way to get an email app, go to www.getjar.com from your phone and search for google mail or any other email provider you might have then click to download and go to installations on your phone and you are ready to go. Also, you can try at ovi too. Other solution is backup your data then format your phone and update its software and apps, that way you get your email on there for sure but trouble is you wont have the apps you had installed so you have to re-download.
I endured all that but as it is time consuming and stressful formatting and re-downloading I simply could not be bothered with that and just downloaded from getjar. Is a well known website amongst others and is quite helpful.
Can you tell us the model of your phone? If it is a Symbian phone, you may try to update the software of your phone or you may re-install the software of the device using Nokia Suite that can be downloaded here. If this is a Lumia phone, try to update the software using Zune or update over the air by going to phone update on the device.
Hope this will help you.