This is a common occurrence when you are using the WHOIS Privacy Services of your Registrar. ICM Registry sends a membership invitation to every unique occurrence of an email that comes into our system, unless the registrar instructs us otherwise. Most registrar proxy services will use a unique email address for each domain, so we email each.
You only need to complete ONE valid membership application. Once you have a valid membership ID, please send the Membership ID to your Registrar and ask them to associate it to your .XXX domains. The domains will start resolving within five minutes.
If you are considering registering additional names and do not want to receive multiple emails, please have your registrar associate those new domain orders to your Membership ID (token) at the point of registration. This will prevent new email invitations from being sent to you, and will get your domains resolving in the shortest time frame (i.e. five minutes or less).
You do not need a membership for .PORN, .SEX or .ADULT names.