There are several mailing lists which might be interesting to users of xen-tools:
This is a general purpose mailing list, for reporting bugs, asking questsion or making suggestions.
This is the developers' mailing list for communication between the developers of xen-tools.
The xen-tools project at gitorius.org allows you to "watch" the project or single repositories of it for changes which you can also receive by e-mail.
Both mailing lists have a complete archive available online.