The idea is essentially to be able to create a deterministic email addresses as an pre-filter whitelist of sorts. Instead of giving out your email address bob@proton there would be a deterministic public key generated for that specific user.

50d858e0985ecc7f60418aaf0cc5ab587f42c2570a884095a9e8ccacd0f6545c@proton, as an example. (SHA256 in this example)

The scenario would be, if you were filling out an online form you'd generate a new email for that vendor. If you begun to receive spam, or someone else got a hold of your email, you know where the leak was because only the first entity should have the key. (Similar to a receive code for bitcoin) Protonmail would know where to send the email, because you're generating it and adding it to their databases similar to an alias, and people or bots trying to choose random keys would be stuck guessing insurmountable odds.

This system would allow reporters (And others) to share emails with more privacy, and puts the ability to "cut the tie" on the receivers side by flagging that address as not valid anymore. (If someone got a hold of an email and dox'd you, you could simply void that key/email) QR codes would be best, as you could share both the email and public encryption key at the same time. (Filling out a paper form at the hospital would be annoying, but still would work)

Hello! i want to know if you are in support of this E-Mail Prizes 2019 ANNUAL DRAWING OF PRIZE FOR E-MAIL USERS

International association of e-mail providers ? It is boldly written on the website that you are in support of it. Over 1000 cash prizes in the amount ranging from $100 to $40,000 to be won.This what they wrote:

More details about the ongoing prize drawing:

International association of e-mail providers EMX (R)

together with largest providers of e-mail services, carries out annual marketing action of loyalty for stimulation of demand and rising the interest of consumer towards this type of service.

This prize drawing is carried out annually since the year of 2010.

ВIn the world, there are registered milliards of e-mail addresses and every day hundreds of thousands of new e-mail addresses get registered.

Automatic system association of EMX (R), randomly chooses e-mail addresses and notifies its owners that they can participate in prize drawing that offers an opportunity to win valuable and cash prizes. see this: Use the following email address to contact support:
paytransfer@protonmail.com Please give feedback as soon as possible.
Thanks.

I have another email service that allows users to schedule draft emails to be sent at a specified date/time in the future. Once the draft is complete, the email is automatically sent at the future specified date/time, unless that draft email is deleted/replaced prior to the send date/time. The draft email can either reside in an existing "draft" folder or a separate "outbox" folder (as distinguished from "draft" that does not have a scheduled send date/time).

Different Emphasis from Similar Postings:
I noticed a number of other similar postings, however, I wanted to provide this new posting to possibly emphasize something more than what I saw emphasized in other similar postings: closely related general delivery options. I would suggest ProtonMail allow every draft email to have a drop down menu that provides the option for selecting "Delivery Timing" using a calendar display for selection of a date and a time field to select/enter a corresponding time on that selected date (time should be clearly set for a selected time zone, e.g., CST or GMT, to reduce possibilities for confusion on timing). Again, whenever "Delivery Timing" options are selected, the draft email can then reside either in the existing "draft" folder or in a newly appearing "Outbox" for any pending emails to be sent at a future date/time. The other email service I use provides a range of closely related general delivery options to also include:
-- "Message Priority" (Low, ******, High);
-- "Private" (to help prevent email forwarding, if clients support that);
-- "Return Receipt" and
-- "Delivery Timing" (previously addressed)
I recommend ProtonMail make these general delivery option menus accessible via one additional icon next to the existing row of icons on draft emails for "Attachments," "Encryption" and "Encryption time." The icon could be a clock next to a letter (just a suggestion), since "Encryption time" already uses a clock icon.

I don't believe other similar postings emphasize these closely associated general delivery Options. I have previously given this other email provider feedback on perfecting their services in other areas (with different providers having different strengths/weaknesses), but this is one particular feature they have had for a very long time that I believe provides an excellent example to follow.