How to delete an email from a used Iphone 4?

I recently bought a used Iphone 4 from Kijiji. The recent owner didn't delete their email account from the phone and it is still in the phone with all the contacts etc. Is there anyway to delete the email without the password?

You could reset the phone to factory settings in settings. Or see if there's a way to log out.

Since he basically just gave you the phone without restoring it (hopefully it not being on iOS 7*) you could do a restore to wipe the phone entirely & then you could sign into your (should be ready to go) Apple ID & continue from there.

*I say hopefully not on iOS 7 due to its Activation Lock feature which prevents someone from activating the iPhone without a proper wipe of the previous Apple ID associated with it in cases of theft or loss. If that is the case should get into contact with the previous owner to either have him/her do a proper wipe of the device or provide the credentials necessary.