220-elvis.mu.org ESMTP Postfix
521-5.5.1 Protocol error
521 5.5.1 In case of permanent delivery errors (e.g. 5XX SMTP errors) please make sure that your mail system is not broken. If you cannot fix it try sending a problem report from a non-blocked location (e.g. gmail/yahoo) to postmaster@mu.org and include the following information: time (Mar 29 08:49:54) and client (224.91.249.125).