No, you are going to go in and delete the mail account itself. Go to Settings>Mail>Accounts>the tap on your Comcast Account. On that page, you should see a Delete Account button. Go ahead and delete it there. Then power the iPhone off and back on again. Go back to that Settings>Mail>Accounts>Add Account. Select Other. Tap Add Mail Account. Put your name in, then your Comcast email address, your password, that you use to access the account in a browser, and where it says description, how you want it to appear on the iPhone. When you tap on Next in the upper right corner, it should go through verifying. If all the checkmarks come up, then you should be able to finish. If you cannot get mail there, then we can check all of the individual settings for your SMTP server after that.