More notes on Comcast: Richard Jackson CoFounder of Aroq Ltd wrote in asking if any addresses with an "att" in them were affected besides the attbi.com ones. Sarah Eder of Comcast just told me none are with the exception of "@broadband.att.com" which is an address that was used only by employees of AT&T Broadband who have now all either been fired or been moved to jobs at Comcast with entirely new email addresses. No, she doesn't think anything sent to their old addresses will be forwarded automatically; if they are on your list the names are probably bad and you'll need to get them to opt-in again with a new address.

People with other ATT email addresses, such as @worldnet.att.net, @attglobal.net and @att.net should not be affected by the Comcast name change because they were not broadband customers.