Although Microsoft doesn’t recommended any particular RBL (Realtime Block List) provider for use with Antigen products, Spamhaus is one of the most widely-known providers on the market.
It’s come to our attention recently that Spamhaus has phased out the old SBL-XBL list, which has now been replaced by the ZEN list (named after a guard dog).
Here’s a comparison of the currently available Spamhaus lists (source: www.spamhaus.org):
Antigen RBL entry
Spamhaus Block List (SBL)
Direct UBE sources, spam services and ROKSO spammers
Exploits Block List (XBL)
Illegal 3rd party exploits, including proxies, worms and trojan exploits
Policy Block List (PBL)
Non-MTA IP address ranges set by outbound mail policy.
ZEN Block List (ZEN)
All 3 SBL, XBL and PBL lists combined
So, what does this mean for you as an administrator of Antigen?
If you’re already using Spamhaus as a RBL list in some way, you need to decide whether to use only the ZEN list, or a combination of the SBL, XBL and PBL lists. Really, if you are happy with blocking the content of all 3 lists, it makes sense to go with Spamhaus’ recommendation of using just the ZEN list. This will improve your lookup responses, as you’ll only need to make one lookup per mail, rather than a potentially 3 lookups (one per SBL, XBL and PBL list).
You should also delete any SBL-XBL list that you have enabled (sbl-xbl.spamhaus.org), since it is no longer in use. This is important to do; otherwise it can cause delays while Antigen is waiting for the corresponding RBL lookup to come back.
Note that Spamhaus provides a free service to smaller customers only. Before using Spamhaus as a RBL service within Antigen, please check to see if you qualify for free usage on the Spamhaus DNSBL Usage page. Otherwise you’ll have to get yer wallet out...