I see there have already been two other issues opened with the same problem in the past couple of days (one of them in the ADOM @ Steam sub-forum): no email is received after creating an account from the game. The same thing has happened to me, and after asking around in the Discord, it would appear there is not supposed to be a long wait for the email.
Now, @jt has already replied to one such issue in this sub-forum, but I am writing now to indicate that this does not seem to be an isolated case as there have now been multiple people with this exact issue happening in quick succession, while a quick search revealed virtually no such threads in the forum before.
Thank you for anyone who would be looking into this, and/or helping to resolve my case in particular (if it is just some bad luck with a rare issue popping multiple times recently).