It turns out I was not entirely innocent of typos after all. Although I am not entirely sure why this should be the case, there was a line in my Sid exim4 config file that was commented out, and when I placed it in the equivalent Sarge file I had not included the hash mark, so it became active and prevented the authentication from working correctly. Commenting out that line allowed it to work, and so a flood of test messages from my Sarge box to my Sid box took place. The line was: AUTH_CLIENT_ALLOW_NOTLS_PASSWORDS='true' -- The Moon is Waning Crescent (1% of Full) But you can still get downloads from http://www.mhcable.com/~chuckh
