This indeed is a behaviour that shouldn't appear at all. But I've to admit that I've never experienced something like this myself so far - the longest time it took for a mail to be received by vivaldi webmail was about an hour.
Did you tested to send yourself some mails from your other mail accounts to see if this is still a problem?
I just send you a test mail to see if this issue is still existent.
I got it immediately. I think there is no problem anymore right now. But in fact, I wasn't aware there was a problem at all before all those 'old mails' suddenly appearing, as I couldn't know I was missing some mails.
If I only got the confirmations mails requested the previous day in my inbox, I will certainly have concluded that the problem came from the site where I wanted to register.
But here it looks like something really weird has happened with my account/on the vivaldi mail side.
@smurf You can talk to @gaelle in private.
You go on her profile and send a message.
I've seen users talking about it, it's still not possible to change the address through the settings. I have also tried to change going in the settings, maybe in the future the users will be able to ...