I want to use a distribution list feature to forward mails directed at all@my-custom-domain.tld to my family members. Several workarounds are not a fit:

a) in the forwarding feature, the recipient is not allowed as a condition so I need to forward all mails. Conditions are only sender, subject, attachment. (related feature request: https://protonmail.uservoice.com/forums/284483-proton-mail-calendar/suggestions/47517764-add-the-recipient-as-a-condition-for-auto-forwar)
b) a sieve filter doesn't work, since it can't forward (related feature request: https://protonmail.uservoice.com/forums/284483-proton-mail-calendar/suggestions/48561584-add-a-forward-email-option-to-filter-actions)
c) I can't change the subject with a sieve filter (editheader is not supported) so the forwarding feature would pick it up.

Only option left is to create a separate account for each distribution list and forward all its mail. But I'd rather not create another proton mail account for this.

EDIT: I discovered I was wrong and workaround a) works for me: If you only want to forward emails sent to a single alias, you select that alias as the "sender". Proton will forward only the emails for this recipient (to:, cc:, bcc: are all considered).
The problem in my tests was, that I had sent the test emails from the same Gmail address as the forward rule target. Somewhere in between, the email is dropped. Presumably by Gmail to avoid endless forwarding loops. Thus, better run your tests from a third account.

I tried the solution recommended below by Alvin T. It may have worked at one time, but didn't function as advertised when I tried to test it.

I'll try setting up a free proton account with the distribution list name and try to auto-forward every incoming message from there to the desired distribution targets.

I somehow managed to create a distribution list a couple months ago. Unfortunately I don't recall how, but it's a real list, not an email forwarding workaround. Today I went to update the list, and whatever worked before isn't out there now.

Did Protonmail slip up and somehow make it available as a beta? I don't know, but it's gone now. I agree with others that this is so basic to an email system it's an absolute requirement.

For organizations and families the usage of either Distribution Lists (at minimum) or even better Shared Inboxes (https://protonmail.uservoice.com/forums/935538-accounts-payments/suggestions/34619938-shared-inbox) is crucial. Creating a strange account which just exists to forward emails to other accounts is really like 1990. I understand the concerns of security here. This why we love Proton, but I really like to see this essential feature for Email rather than another new product, at first.

Is this not the same as Contact Groups?

This is an absolute requirement and I'm shocked that this feature doesn't exist. I cannot use Proton for Business without this feature and will recommend to others to find a different email provider.

Email forwarding is NOT a solution for this issue. A proper distribution list can be managed by multiple people, etc. I will likely migrate away from Proton due to this very, very basic missing feature. My partner is kinda ****** off about moving from google workspace to Proton, primarily due to missing basics like this one.

I need something that would allow external users to send email to. A use case for this would be "support@domain.com". "support" would be a list that contains existing users. Once the email comes in, it's distributed to all those users.

To make things easier, the users don't need to respond as "support@domain.com".

Another use case. Oftentimes I signup for services using these lists as roles. Example: "zapier@company.com" is the zapier account that is used by the organization.

This has been completed with this change:

https://proton.me/support/email-forwarding

Now you can create an email address for your organization (or family) then set it to forward to as many or as few addresses as you want, apply rules, etc...

It's not the perfect solution, but it's a good one.

This a basic feature for any enterprise.

I migrated to a Proton Family plan with custom domains and I had to set up a catch-all to get mail for distribution lists in the old email system. This works but is obviously not idead.

Deal breaker feature. Most businesses cannot operate without it. ERP systems are commonly set up to send to ***@company.com for one notification, then YYY@company.com for another notification, etc. They don't modify each of several hundred notifications. Instead they just modify members of ***@company.com and YYY@company.com.

I would really like to at least hear from Proton if this is a feature which might appear an some point of time. For companies this is NOT a nice to have feature. To consider Proton mail this needs to be there at first.

Is the team at least aware of it an is planning to implement it?

Is the reverse of this working, so you have an inbound alias that goes to a group of internal users ?

I do have protonmail but this could be a deal breaker when it is time to renew my subscription. This is one of the most important feature for a business to email to our clients.

Important and basic function…

This is one very importand item for me to switch from Google to Proton as my wife and I use a combined emailadress receiving and sending emails from it.

It's fairly basic for any email system

As many others have said, this is critical for most all organizations and blocks wider-scale adoption of ProtonMail. Even as a non-organization it's getting in my way since I use distribution lists for my family.

Dear ProtonMail, I love you in principle, but with the flood of people about to quit g-suite, it's a pity you don't have this feature already. I will have to set up a subdomain and a mail server to forward inbound message to "support@help.example.com" to the people who need it, in my example.com organisation. But it's a bit of a kludge, it would be great if you could do this natively in your cool server room deep beneath the Alps.