mail.log had no logrotate rule and grew unbounded to ~1GB (~150MB/day)
since Jun 8. This host logs via Postfix's built-in postlogd (maillog_file
mode), not rsyslog (no rsyslog.service exists), so postlogd holds the file
open -- a plain rename+create would leave it writing to the stale inode.
Use copytruncate (no daemon signal needed). Rotate daily, keep 14 days
compressed. Applied live: forced first rotation, compressed the 1GB
archive (->99MB), verified logging + bounce watchers + DKIM signing intact.
Part of the email-deliverability incident hardening (follows DKIM fix 4d59019).
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