So there is big fuzz about the Linden Lab mailservers being blocked by the SPAM protection real-time-blacklist spamhaus.org - and of course the usual suspects try to blame it all on Linden Lab. And while it seems some configuration options on the LL mailservers might indeed be set different to avoid such problems, for me the real problem is with spamhaus.org
I had the dubious pleasure to deal with spamhaus.org in the past, and it cost me lots of time and energy and in the end a whole mailserver had to be moved to a different IP address. Spamhaus is known to be quite trigger happy and in their self-righteousness try to "educate" (read: coerce) mail service providers. Just search Google for "spamhaus blackmail" and you will find many more hits than a credible service should get.
Realtime blacklists are an efficient method to prevent the distribution of spam. But with my past experience, and with the reports from others, I can only discourage people to use the services of spamhaus.org. There are other services around, for example spamcop.net which relies on manual tagging of spam by other users.
But Linden Lab is NOT to blame for this!