Announcement List admin screen doesn't show all domains

In my control panel, on the Announcement List set up screen, the list of domains in the pulldown for the “Email address of the list” field shows duplicate domains and some domains I host are missing. The domain I want to set up an announcement list for is not showing.

Does anyone know how this list of domains is generated or how I can edit it? BTW, the list of domains for the discussion list admin screen looks fine (no dupes, nothing missing).

Thanks,
Steve