I would love to change my e-mail address to a more secure one and created a Mailfence e-mail address for that. Steam apparently does not support Mailfence (at least not for changing the e-mail address to it, I read in another thread). It would be good to know which e-mail providers are accepted and which are black-listed.
I was not able to contact Steam Support for that because every account issue just gets redirected to the account managing page when trying to reach support through the support page.

Anyway, I thought I might ask the community. Do you know secure e-mail providers that are accepted by Steam? Maybe it would be beneficial to have some kind of list of which ones work and which ones don't.
I found these two resources that might explain the Mailfence issue (or try to) but don't really offer alternatives.
https://gtm.steamproxy.vip/discussions/forum/1/3543798390545352807/
https://gtm.steamproxy.vip/discussions/forum/1/3875966763782442561/

Also if you have thoughts or updates regarding Mailfence specifically and this weird relationship with Steam, that would also interest me since it has a growing user base that is intrigued by its security measures.