I'm currently on one of the large IT company's email provider. It's driving me nuts as it's constantly thinking there's suspicious activity on my account, probably because I'm using TOR, and then challenges me with a code it texts to my phone. And then every once in a while it thinks my password might be compromised and makes me change it. I never want to be forced to change my password. I will handle the security (password) for my account.
They also read my email as I've received calendar reminders of an upcoming flight and there's no way they would have known that without reading my email. They of course think they're doing me a favor, but I don't need any favors from them. I'd rather they not have access to my emails.
And I don't mind paying a reasonable amount for a good secure email provider who believes in privacy.
I found this site and it appears to have some good info:
sms is a cell phone for text messaging. The idea here is everyone who has a cell phone has a unique phone # (primarykey), which is mostly only used by that person.
This is why they request SMS #'s and reject home phone #'s (which are weaker links to people since many people can use them - big tech wants those primarykeys because the likelihood of identifying you is high)
TempSMS = burner sms # websites you can find by searching for "temporary sms", and plug in, and hope they work (it's mostly miss, but you can sometimes get a hit after a lot of persistence).
Note: cell phones also have IMEI (phone hardware) and SIM (telco card) numbers too which could be used to find the purchaser (you). So the best bet is to never use a cell phone, they are tracking devices in more ways than one.