Why won't Steam accept Mailfence for emails?

[sappyguppy]

I need to change my email for steam. (my yahoo account was just blocked behind a premium paywall) I would like to use Mailfence which is known for extreme security and privacy policies. I've used it for all my financial and utility information, so it obviously is very well vetted. Unfortunately, steam will not accept it.

Does anyone know why?

I don't want to switch to gmail or some other commerical email service (gmail, hotmail as examples) for privacy and security reasons. Do I have a choice on this matter?

If Mailfence is unacceptable, can someone suggest an email service acceptable to Steam that has a similar take as Mailfence towards user's security and privacy?

And, finally, will having my steam account associated with an unaccessible email account interfere with my currently owned games and future purchases?

Thanks

[nullable]

https://steamcommunity.com/discussions/forum/1/3543798390545352807/

Seems like last year there were some issues last year. While the testing results may be better, there may not be enough demand for Valve to whitelist that provider.

I don't have any specific recommendations for alternatives though. I just use gmail like a sucker.

[Cathulhu]

Still lacking TLS support over SMTP. Simply bad practice.

[Azure Fang]

Have you tried Proton Mail?

[Muppet among Puppets]

For proton mail, you should have had at least once a paid plan. That way your account wont be deleted for inactivity (12 months).