The package as shipped ensures that the configuration file is not a
symbolic link.  This is most likely unnecessary, as I don't believe
there is any security risk in reading from a symlink.

Changing 'lstat' to 'stat' on line 170 of parser.y fixes this.  I've
attached a patch.

I keep my configuration files in a version-controlled directory,
~/etc, and symlink them into ~/.  esmtp is the only package I use that
complains about this arrangement.

(This is the first bug I've reported to Debian.  Please let me know if
I've messed up somehow.)