[Dovecot] dovecot not logging after upgrade to 2.1.7 on debian

[Steinar Bang]

After upgrading my IMAP server to the new debian stable, and upgrading
dovecot from 1.x to 2.1.7 in the process, dovecot no longer logs
anything to /var/log/mail.*.  The last entries there are from before the
upgrade, and no starts or error messages or failed login attempts, since
then, have been logged.

Does anyone know what might cause this?

"doveconf -n" doesn't mention any of the log settings.  Maybe the log
settings aren't picked up?  What could be done to make sure they are
picked up?

Here's the content of the /etc/dovecot/conf.d/10-logging.conf file:

##
## Log destination.
##

# Log file to use for error messages. "syslog" logs to syslog,
# /dev/stderr logs to stderr.
log_path = syslog

# Log file to use for informational messages. Defaults to log_path.
#info_log_path = 
# Log file to use for debug messages. Defaults to info_log_path.
#debug_log_path = 

# Syslog facility to use if you're logging to syslog. Usually if you don't
# want to use "mail", you'll use local0..local7. Also other standard
# facilities are supported.
syslog_facility = mail

##
## Logging verbosity and debugging.
##

# Log unsuccessful authentication attempts and the reasons why they failed.
#auth_verbose = no

# In case of password mismatches, log the attempted password. Valid values are
# no, plain and sha1. sha1 can be useful for detecting brute force password
# attempts vs. user simply trying the same password over and over again.
#auth_verbose_passwords = no

# Even more verbose logging for debugging purposes. Shows for example SQL
# queries.
#auth_debug = no

# In case of password mismatches, log the passwords and used scheme so the
# problem can be debugged. Enabling this also enables auth_debug.
#auth_debug_passwords = no

# Enable mail process debugging. This can help you figure out why Dovecot
# isn't finding your mails.
#mail_debug = no

# Show protocol level SSL errors.
#verbose_ssl = no

# mail_log plugin provides more event logging for mail processes.
plugin {
  # Events to log. Also available: flag_change append
  #mail_log_events = delete undelete expunge copy mailbox_delete mailbox_rename
  # Available fields: uid, box, msgid, from, subject, size, vsize, flags
  # size and vsize are available only for expunge and copy events.
  #mail_log_fields = uid box msgid size
}

##
## Log formatting.
##

# Prefix for each line written to log file. % codes are in strftime(3)
# format.
#log_timestamp = "%b %d %H:%M:%S "

# Space-separated list of elements we want to log. The elements which have
# a non-empty variable value are joined together to form a comma-separated
# string.
#login_log_format_elements = user=<%u> method=%m rip=%r lip=%l mpid=%e %c

# Login log format. %$ contains login_log_format_elements string, %s contains
# the data we want to log.
#login_log_format = %$: %s
 
# Log prefix for mail processes. See doc/wiki/Variables.txt for list of
# possible variables you can use.
#mail_log_prefix = "%s(%u): "

# Format to use for logging mail deliveries. You can use variables:
#  %$ - Delivery status message (e.g. "saved to INBOX")
#  %m - Message-ID
#  %s - Subject
#  %f - From address
#  %p - Physical size
#  %w - Virtual size
#deliver_log_format = msgid=%m: %$