If neither box is "ticked" then that means that you *had* selected the mailing list but that it was disabled because, for some reason, the mail was bounced. This might be because your mailbox was full one day or your mail server was down, or perhaps something "further from home" hapened--perhaps DNS server(s) were down and the mail couldn't be delivered to your mail server.

In any case, just re-select the mailing list option and you'll be good to go.

Craig Steiner