Please update Mailr to the latest revision from the subversion repository. There is a new configuration option called "imap_auth". It is used to specify the authentication method used to connect to the IMAP server. The default value is "PLAIN" which works for Courier IMAP but I guess that some IMAP servers do not support "PLAIN" so in this case you can try to set "LOGIN" method. To do so you have to add the following line to your config/site.rb file:
:imap_auth => 'LOGIN'
It is possible to cause mailr to send a "login" command now. Could you please update to the latest revision and add the following line to your config/site.rb file:
:imap_auth => 'NOAUTH'
Add the following line to your config/site.rb file:
:send_from_domain => 'your_domain'
Update Oct 2007: Those two patches for imap.rb fixed the problem for me:
http://shugo.net/tmp/imap-no-body-fld-md5.diff
http://dinhe.net/~aredridel/2007/09/28-imap/imap-delivery-failure.patch
Update: Ticket is created for this problem on RubyForge by Brian Skahan (see http://rubyforge.org/tracker/?group_id=426&atid=1698&func=detail&aid=3983)
Add the following line to your config/site.rb file:
:debug_imap => true
You should be able to see the debug messages of Net::IMAP on stderr (if you are using Webrick you will see the debug messages on the console).