Looks like they ignore anything in this community. And if you report an error in the app, they just redirect here to ignore you...
I have yearly subscription, but now I'm seriously considering moving out. So many basic functionalities are missing it's maddening. What's even the point of using aliases, if you can't define the alias in the reply-to?
And the best part - this was reported in 2018!!!, almost 6 years ignoring their customers without any response from the Proton team! Great job! All good since you get your money already, right?

Also, to add to all the above, they added pointless LLM cr.ap, instead of working on actual useful features...

Dear Proton Team, any plans or news to share on this?

What I find maddening about this issue is that Proton refuses to even respond as to why they cannot/ will not implement this. As everyone here has already mentioned, this is standard fare in every other legitimate email client out there - and has been for years.
I use duck.com as my primary email address to strip out trackers and then forward to my proton address. The lack of a "reply to:" header defeats the purpose

This option would be curtail, otherwise I don't see any use for catch-all service

Regarding "...I suspect that they have not implemented this because doing so completely eliminates end-to-end encryption,..." IF this is their rationale, I disagree with their logic. Like you, I have a professional association but those emails (and those I select reply-to to that address) are not privacy sensitive and I don't want those recipients to use my Proton address. I just want to use a single mailbox for both.

I too have an eternal email address from a professional society where I'm a lifetime member. I've used that address for nearly 30 years where it has pointed to various mail systems over time. I assumed that Proton would have this functionality as well, as it's just so basic, so I'm really shocked it does not. Now feel bad that I got a paid account before finding this out. I suspect that they have not implemented this because doing so completely eliminates end-to-end encryption, but the fact that they have not said as much does not speak well for them, and that could be dealt with through simply informing the users -- I want to be able to make an informed choice between confidentiality and availability.

Yes, why isn't it possible to add a reply-to field?
I even wish to be able to set it as a default under user preferences.

Will this come? I have an "eternal mail address" with a forwarder service, and I want people respond to that mail when I send mails from Proton. Anything in the pipeline?

In all other mail programs adding a reply to header to your outgoing mails is quite standard, which brings me to the question why is it inpossible to set one in Proton? Sales has told me Proton has no intention to implement it at all, I would like to know why. Instead they suggest that I set a forwarder, but that is not what I asked for.

Given how long this issue has remained open, there must be some real or imagined reason that Proton won't implement it. Is there perhaps a security issue? Proton, please at least comment.

Need this to include send from aliases
Example test.com alias to proton account
Send from j@test.com with a reply to of john@test.com

Hello, it's a simple feature : every mail provider has it.

II have two email "presences" that I need to maintain on outgoing emails, as an editor and as a licensed radio amateur. I need to be able to invoke a "reply-to" link for selected outgoing email messages. It works fine in gmail. I'd like to switch to proton mail for everything but I cannot without a selective "reply-to" choice.

Proton does not use the Reply-to: header of the email.

We use a webform in the contact section. Emails are sent from site@customdomain.com to site@customdomain.com with a Reply-to: header of customer@someone.com
When pressing Reply, it should see the Reply-to: header and send to the customer. Instead if sees it's sent from site@customdomain.com and replies to site@customdomain.com

Gmail Reply-to: headers work fine with the same forms.

If you send mail via Proton Mail Bridge with a Reply-To field, it gets stripped off. This suggests this is a deliberate lock-in policy. Not good.

We need it please !
Especially when you can't use imap with a Proton account

Just signed up for a Proton mail account and very disappointed not to have this feature.
This has been reported so often that Im surprised that Proton refuses to offer it.
I will continue to search for another alternative to Gmail that does. Good thing I did not already choose the paid Proton service.

The fact that this is not implemented is shameful.

Special handling for Reply-To is not critical, but being able to add standard email headers definitely is. There's no good reason not to have an escape hatch.

Here too.