Sorry, once you join this list there is no getting off.
Actually, I have experienced the same thing that you are describing. I
have unsubscribed myself several times when I knew I was going to be
traveling and wanted to avoid the extra mail traffic. Each time, XMCA
re-subscribed me after a short period of time with no action on my part.
The first time this happened I thought that the system administrator had
reverted to a backed up subscriber list, but this has now happened to me
more than once. ---Tim