- Verizon (which includes AOL, Yahoo, Compuserve, Verizon, etc.)
- Microsoft (Microsoft OLC, aka outlook.com or Hotmail), and
- Google (Gmail).
Verizon (AOL, Yahoo, Verzion) domains: aim.com, aol.at, aol.be, aol.ch, aol.cl, aol.co.nz, aol.co.uk, aol.com, aol.com.ar, aol.com.au, aol.com.br, aol.com.co, aol.com.mx, aol.com.tr, aol.com.ve, aol.cz, aol.de, aol.dk, aol.es, aol.fi, aol.fr, aol.hk, aol.in, aol.it, aol.jp, aol.kr, aol.nl, aol.pl, aol.ru, aol.se, aol.tw, bellatlantic.net, citlink.net, compuserve.com, cs.com, frontier.com, frontiernet.net, games.com, goowy.com, gte.net, love.com, netscape.net, rocketmail.com, rogers.com, sky.com, verizon.net, verizon.net.in, wild4music.com, wmconnect.com, wow.com, y7mail.com, yahoo.at, yahoo.be, yahoo.bg, yahoo.ca, yahoo.cl, yahoo.cn, yahoo.co.hu, yahoo.co.id, yahoo.co.il, yahoo.co.in, yahoo.co.jp, yahoo.co.kr, yahoo.co.nz, yahoo.co.th, yahoo.co.uk, yahoo.co.za, yahoo.com, yahoo.com.ar, yahoo.com.au, yahoo.com.br, yahoo.com.cn, yahoo.com.co, yahoo.com.hk, yahoo.com.hr, yahoo.com.mx, yahoo.com.my, yahoo.com.pe, yahoo.com.ph, yahoo.com.sg, yahoo.com.tr, yahoo.com.tw, yahoo.com.ua, yahoo.com.ve, yahoo.com.vn, yahoo.cz, yahoo.de, yahoo.dk, yahoo.ee, yahoo.es, yahoo.fi, yahoo.fr, yahoo.gr, yahoo.hu, yahoo.ie, yahoo.in, yahoo.it, yahoo.lt, yahoo.lv, yahoo.ne.jp, yahoo.nl, yahoo.no, yahoo.pl, yahoo.pt, yahoo.ro, yahoo.rs, yahoo.se, yahoo.si, yahoo.sk, yahoogroups.ca, yahoogroups.co.in, yahoogroups.co.uk, yahoogroups.com, yahoogroups.com.au, yahoogroups.com.hk, yahoogroups.com.sg, yahoogroups.de, yahooxtra.co.nz, ybb.ne.jp, ygm.com, ymail.com
Microsoft OLC (outlook.com / Hotmail) domains: hotmail.ac, hotmail.as, hotmail.at, hotmail.ba, hotmail.bb, hotmail.be, hotmail.bs, hotmail.ca, hotmail.ch, hotmail.cl, hotmail.co.at, hotmail.co.id, hotmail.co.il, hotmail.co.in, hotmail.co.jp, hotmail.co.kr, hotmail.co.nz, hotmail.co.pn, hotmail.co.th, hotmail.co.ug, hotmail.co.uk, hotmail.co.ve, hotmail.co.za, hotmail.com, hotmail.com.ar, hotmail.com.au, hotmail.com.bo, hotmail.com.br, hotmail.com.do, hotmail.com.hk, hotmail.com.ly, hotmail.com.my, hotmail.com.ph, hotmail.com.pl, hotmail.com.ru, hotmail.com.sg, hotmail.com.tr, hotmail.com.tt, hotmail.com.tw, hotmail.com.uz, hotmail.com.ve, hotmail.com.vn, hotmail.cz, hotmail.de, hotmail.dk, hotmail.ee, hotmail.es, hotmail.fi, hotmail.fr, hotmail.gr, hotmail.hk, hotmail.hu, hotmail.ie, hotmail.it, hotmail.jp, hotmail.la, hotmail.lt, hotmail.lu, hotmail.lv, hotmail.ly, hotmail.mn, hotmail.my, hotmail.net.fj, hotmail.nl, hotmail.no, hotmail.ph, hotmail.pn, hotmail.pt, hotmail.rs, hotmail.se, hotmail.sg, hotmail.sh, hotmail.sk, hotmail.ua, hotmail.vu, live.at, live.be, live.ca, live.ch, live.cl, live.cn, live.co.hu, live.co.in, live.co.kr, live.co.uk, live.co.za, live.com, live.com.ar, live.com.au, live.com.co, live.com.mx, live.com.my, live.com.pe, live.com.ph, live.com.pk, live.com.pt, live.com.sg, live.com.ve, live.de, live.dk, live.fi, live.fr, live.hk, live.ie, live.in, live.it, live.jp, live.lk, live.mk, live.nl, live.no, live.ph, live.ru, live.se, msn.cn, msn.co.nz, msn.com, msn.net.au, outlook.at, outlook.be, outlook.bg, outlook.bz, outlook.cl, outlook.cm, outlook.co, outlook.co.cr, outlook.co.id, outlook.co.il, outlook.co.jp, outlook.co.nz, outlook.co.th, outlook.com, outlook.com.ar, outlook.com.au, outlook.com.br, outlook.com.cn, outlook.com.es, outlook.com.gr, outlook.com.hr, outlook.com.pe, outlook.com.py, outlook.com.tr, outlook.com.ua, outlook.com.vn, outlook.cz, outlook.de, outlook.dk, outlook.ec, outlook.es, outlook.fr, outlook.hn, outlook.ht, outlook.hu, outlook.ie, outlook.in, outlook.it, outlook.jp, outlook.kr, outlook.la, outlook.lv, outlook.mx, outlook.my, outlook.pa, outlook.ph, outlook.pk, outlook.pt, outlook.ro, outlook.sa, outlook.sg, outlook.si, outlook.sk, outlook.uy, webtv.net
Google domains: gmail.com, googlemail.com
Keep in mind that no externally-compiled list like this is going to be perfect.
I used 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. Check it out -- it contains extra features.)
How is this data differently compiled versus what other people might put together? I am not checking some master list of 25 million known domains to group domains by MX records that point at an Verizon or Microsoft server. I'm restricting checking to a small number of possible domain name choices. This way I'm avoiding the common problem where, when compiling data like this, you end up with five million small business domains whose mail is hosted by one of these companies but they shouldn't be counted as a consumer mailbox domain.
I don't have proof that every one of these domains actually houses consumer mailboxes for that given webmail provider, so the list for Verizon 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.
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.
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 choose to use the domain googlemail.com instead. 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.