I'll take your question to mean that you don't want to get emails in your Comcast email account--------right? If that is the case, then on the Inbox page click on the gear icon in the upper right corner of the page, then on Settings. On the landing page Under Mail, click on "Advanced settings". On that landing page under "Safe list", check the box to enable it. You will be prompted to enter an email address. Enter your own email address, then click on "Add".
Once that is done, you will no longer get emails from anyone other than yourself if you choose to send yourself one. The Safe list only allows emails to get to your Inbox from email addresses that you put on that list. Nothing else will get through.