I made a list of some of uptilt.com (emaillabs.com) customers':
http://www.emaillabs.com/clientlist.html
likely domains:
http://spamcheck.freeapp.net/whitelists/uptilt
and checked those domains against all existing SURBLs. The only matches were:
uptilt.com
on ws.surbl.org, due to Chris' earlier manual listing, and:
digitalimpact.com uptilt.com wordbiz.com
on ds.surbl.org (6dos) which is a pretty low hit rate for nearly a hundred domains against a fairly aggressive list *if uptilt.com were a spamhaus*. It's not totally conclusive, but the relative lack of inclusion across multiple SURBL data sources leads me to think that uptilt.com is probably not a spamhaus. Therefore I've used that list of uptilt.com domains and customer domains as a whitelist. That means they will not be included in SURBLs.
Jeff C.