At a guess, your mailer is configured to use "rich text" or "HTML" mail; the mailing list will only handle text/plain messages, either as the only content or as part of a multipart/alternative.

-- 

brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com

system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu

electrical and computer engineering, carnegie mellon university    KF8NH