Two applications add SURBL support to Sendmail and MailEnable respectively:
Anthony Howe of SnertSoft reports that his milter-link/0.1 for Sendmail "extracts URLs from the message body (text, HTML, and/or MIME encoded)" and checks them against SURBLs, or after domain resolution against RBLs. Written in C, milter-link does on-the-fly MIME decoding without using temporary files.
http://www.snertsoft.com/sendmail/milter-link/
Martyn Keen reports that his MEFilter, a bolt-on for the MailEnable mail server, adds beta SURBL support. Test results are very favorable.
Cheers,
Jeff C.