Okay, so we are talking about configuration rather than registration. Sorry for being nitpicky here. 
And yes, correct configuration of the e-mail server is up to Bitwarden.
However, not getting the validation code I cannot move to my new work machine.
I changed the e-mail address of my vault a few days ago and I cannot remember a required confirmation to the old address. So I would suggest to perform a backup of your vault and just try to change the address.