Here's another idea: why not use Namecoin [1] to keep the data? It's fair, no one owns it, and everyone can query it.
[1] http://bluishcoder.co.nz/2011/05/12/namecoin-a-dns-alternati...
[1] http://bluishcoder.co.nz/2011/05/12/namecoin-a-dns-alternati...
What about a simple proposal for the convention of firing a query for a mailing address before each mailing, by such means as:
1. HTTP request to (something like) "/address.txt"
2. *blank* email with subject line (such as) "address"