Upgrading Debian Etch to Lenny

Debian Etch has been serving me well for a few years with wonderfully easy and infrequent maintenance.

However it's at the end of its life

http://www.debian.org/News/2010/20100121 [1]

So I've upgraded to Lenny following these instructions

http://www.debian.org/releases/lenny/i386/release-notes/ch-upgrading.en.... [2]

It was remarkably painless

One small problem with the mail system.

Errors were encountered while processing:
 exim4-config
 imapproxy
 exim4-base
 exim4-daemon-light
 courier-imap
 at
 bsd-mailx
 courier-imap-ssl
 mailx

But scrolling upwards I got a more helpful error message

A package failed to install.  Trying to recover:
Setting up exim4-config (4.69-9) ...
DEBCONFsomethingDEBCONF found in exim configuration. This is most probably
caused by you upgrading to exim4 4.67-3 or later without accepting the
suggested conffile changes. Please read
/usr/share/doc/exim4-config/NEWS.Debian.gz for 4.67-2 and 4.67-4

So I purged exim, deleted the config files, reinstalled it and now everything seems good.