@renatolond @Siphonay this exact thing happens up to a dozen times a week...still manageable but annoying.
Always uses a string of random characters as a user name. Almost always email addresses of the big public web mail services (Yahoo, hotmail, gmail, outlook). Almost none of them go through with email verification.
Looks like they are using an old list of compromised accounts. Maybe auto delete all accounts that do not verify within 'x' hours to cut back on the garbage sign-ups.