After I send a message to that addressee group by placing the Category name on the Bcc: line (I use my address in the To: line), the message  goes out to those individuals. However, the next day when I open WLM and prepare to send an email to that same group, I place the name of that category in the Bcc: box and click on the plus sign only to find that the email addresses have disappeared.

I found that out the hard way when I received complaints that none of the club members were receiving the meeting notifications. When I go to that category to edit the names, I find that it is empty.