(You might notice that this is a slightly-modified repost of previous content. It was necessary to deal with Blogger suddenly taking issue with a post containing a giant list of domains. Whoops.)
Looking to segment your email database based on ISP? Want to break out separate content or timing for Yahoo Mail versus Microsoft OLC versus Gmail subscribers? I’ve got you covered. Click here to download the full “MAGY” (Microsoft, AOL, Gmail, Yahoo) domain list, and feel free to use it for email segmentation. (And please don’t use it for spammy purposes.)
Notes: Yahoo (then Verizon) clarified for me earlier in 2021 that they do not own Yahoo Japan (.jp) -- they license the brand to someone else. So, the Yahoo-related .jp domains are hosted by a different entity, if you want to break those out separately. (I believe those would be yahoo.co.jp, yahoo.ne.jp, and ybb.ne.jp. I do not believe this includes aol.jp -- that domain's MX record seems to point at the typical Yahoo (non-JP) infrastructure.)
Methodology: I wrote a script to generate this list of domains, starting with the commonly known domain part choices for each provider, then I looked up the possible MX record for this domain under every possible country TLD. Meaning, I checked the MX for every possible version of yahoo.*, aol.*, hotmail.*, outlook.* and other variations where I know at least one of those variations hosts consumer webmail. (You can find the script here. Feel free to steal it and use it as a starting point to create a better version!)
I don't have absolute proof that every one of these domains actually houses consumer mailboxes for that given webmail provider, so the list for Yahoo and Microsoft might be a bit bigger than it needs to be. However, better safe than sorry, and there's probably no harm if a few extra domains, also seemingly hosted by each provider, end up in the mix.
Microsoft: A couple of the Microsoft domains are quite possibly not consumer webmail domains, but their domain name is similar enough to ones in use and the MX is hosted by them, so that was another case where I felt it was better to be over-inclusive rather than potentially leave out a few domains that should have been included.
Google: Remember that Google only has two consumer webmail domains: gmail.com and googlemail.com. When Gmail was initially launched in the UK and Germany, Google was unable to secure the "Gmail" trademark and was forced to use an alternate domain, giving us googlemail.com. This was resolved in the UK in 2010 and in Germany in 2012, but users can still receive mail at the "googlemail.com" version of their email address.
Yahoo: AOL and Yahoo were once separate entities, and then later they were combined by Verizon into a brand called “Oath,” later renamed Verizon Media. As of September 1, 2021, both AOL and Yahoo mail is handled by a new corporate entity called Yahoo Inc.
September 18, 2021 Update: I've added "windowslive.com" and "windowslive.es" as additional Microsoft domains, based on a tip from a client. Thanks for the suggestion!