``` bash

MAILU_DATA="/path/to/mailu_data" # Path to Mailu data

BACKUP_DEST="user@synology:/path/to/synology/backups/mailu" # Destination on Synology NAS

BACKUP_NAME="mailu_backup_$(date +'%Y%m%d%H%M%S').tar.gz" # Backup file name with timestamp

KEEP_BACKUPS=5 # Number of backups to retain

LOG_FILE="/var/log/mailu_backup.log" # Log file location

echo "$(date) - Starting Mailu backup..." >> $LOG_FILE

tar -czf "/tmp/$BACKUP_NAME" -C "$MAILU_DATA" . >> $LOG_FILE 2>&1

if [ $? -ne 0 ]; then

echo "$(date) - Backup creation failed!" >> $LOG_FILE

exit 1

fi

rsync -avz --remove-source-files "/tmp/$BACKUP_NAME" "$BACKUP_DEST" >> $LOG_FILE 2>&1

if [ $? -ne 0 ]; then

echo "$(date) - Rsync to NAS failed!" >> $LOG_FILE

exit 1

fi

echo "$(date) - Cleaning up old backups..." >> $LOG_FILE

ssh user@synology "cd /path/to/synology/backups/mailu && ls -tp | grep -v '/$' | tail -n +$((KEEP_BACKUPS + 1)) | xargs -d 'n' -r rm --" >> $LOG_FILE 2>&1

if [ $? -eq 0 ]; then

echo "$(date) - Old backups cleaned up successfully." >> $LOG_FILE

else

echo "$(date) - Failed to clean up old backups." >> $LOG_FILE

fi

echo "$(date) - Backup completed successfully." >> $LOG_FILE

```