It is important to use a login that is not associated with an (main)email address. This is an additional step in preventing password guessing.

I'm so excited this is under review! This is the only missing Proton feature keeping me from fully switching over to Proton for everything and ditching Microsoft and Outlook! Proton, please make it happen!

From a security perspective, it would be ideal to choose which alias can be used for log on and be able to exclude the primary address/username altogether.

Please allow the users choose which email address can be used to log in, so only the primary address and/or selected aliases work. As currently every alias can sign in is a major security risk because leaked or exposed aliases widen the attack surface. Most of us use aliases only for communication, we dont need that to be used for log in.

Important feature.

By far the number one feature I want. I'm shocked it's not already a built in feature - this before all else and I'll even contribute money to a pool to move this issue up if that were an option.

Would like to be able to designate login user id so only 1 can be used.

I think it would also be nice to designate a list of aliases and rotate login Id at a specific time interval so that it is harder to guess.

Should allow a control to limit logins to only primary or selected user IDs.

Please do it now! No question!

I share the concerns expressed by other users. I have purposefully kept my main proton account email secret to limit the attack surface to my proton services. It was a little shocking to learn that logins could be attempted from any proton alias that I use. I hope this will be addressed soon.

Same issue, it's a big security issue.

+1000

This is why I don’t use Proton as my main email: I can’t rely on an address that grants direct access to my most private data.

+1

This is a huge hole/bug imo

Yes please! I can't imagine this would be too difficult to implement. It could be left turned off by default so it wouldn't cause problems for anyone used to logging in with the aliases but would give much peace of mind to those who like that feature on other providers like Microsoft Outlook.

I was going create this request too ! It's very important for security !
Someone with a secondary address will never be able to hack me

I find this feature important for security. One secret address as user name for login and few aliases to share.

What about those of us who use an alias to login to a different device?

For example: I have an alias for my laptop as my main login is used on my phone, and using rules to keep the email in their own folders.
In this case, by restricting access to aliase logins, it would mean that I'd have to either login using the same credentials on each device, or have a second account for my laptop.

Unless there's another option I'm not aware of?

I think this is similar: https://protonmail.uservoice.com/forums/284483-proton-mail/suggestions/47611028-choose-which-alias-can-log-in-to-proton

You are currently able to log in to a Proton service using any of your email aliases. A user should have the option to disable account logins for anything other than their original account username.