Try using a filter. On the Inbox page click on the gear icon in the upper right corner of the screen, then on Settings. Click on "Filter rules" and follow the prompts. There needs to be something consistent with the emails like the same email address, or the same words in the body or Subject and so on. Other than a filter, just keep marking them as Spam if they make it to your Inbox.
I have tried and tried blocking domains using the filter, no no avail. I continue receiving spam from @leparisien.fr. I have cleared all filter, then my system and then rebooted the system. Put in the filters again - same problem, the spam was there in force. I have gone through cutomer service, tech support about this problem in the past, they say they've fixed the problem, but still the spam flows. Instead on continuing to jack up the prices, maybe Comcast should look at improving or at least make their services work properly.