I checked the mail server logs. The website sent the notifications correctly, but Proton temporarily rejected them with: 450 4.7.1 Recipient address rejected: Please try later
Later, Proton accepted the messages successfully with 250 2.0.0 OK.
So the delay was on Proton's side, not the website's mail system.
450 4.7.1 Recipient address rejected: Please try later
Later, Proton accepted the messages successfully with 250 2.0.0 OK.
So the delay was on Proton's side, not the website's mail system.