I have some important files in one of my accounts, they are all registered under the same domain so [email removed as per Community Guidelines], [email removed] and so on but I can't remember the other ones, is there anyway to find out what account I have registered?
I would only be able to suggest a way to check this manually, which would be to try and sign into Dropbox under each of the email addresses that you have access to.
You can request a password reset for these emails too from here if you're not sure which password you could have used. You will only receive an email if a Dropbox account is registered under the email address you enter.
Please do remember to check your junk/spam inbox of your email account though, just in case the email gets redirected there by mistake.