I had the same issue. I had used my comcast e-mail account name to log into Windows 8 and then 10. The Windows 10 mail linked the Comcast account to a Outlook account. To fix, I went into Windows 10 mail, clicked on settings (icon in bottom of leftmost window), selected Accounts (in new pop-up window), selected the Comcast e-mail account, then edited the account to deselect everything and turn the e-mail switch to off. After a restart, I was able to receive all the spam in my Comcast account.
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