If you are already using rsync then consider using your own backup solution like what i recommended instead of using the build in one.
You can set up a crontab on your box to do the rsync regularly manually. crontab -e
Since rsync checks the file hash for changes, you are unlike to get any corrupted files with the services running compared to s3 backup build in solutions.
nano script.sh
#!/bin/bash
rsync -avzh /home/user-data/mail/ /remote/dir/
make script executable
chmod +x script.sh
set up crontab with sudo crontab -e. You need your cron to run as root. add in the follow cron to run it hourly.
0 * * * * /path/to/script.sh > file 2>&1
PS: these backup files are unencrypted (unlike the build in backup), so you must secure it yourself
Edited A better solution would probably be backing up the encrypted files instead as suggested → Backup question,root as owner of backup file - #16 by alento