Is there an easy way to determine how many mails a user has sent

==== Required information ====
- iRedMail version (check /etc/iredmail-release): .0.9.2
- Linux/BSD distribution name and version: (Ubuntu 14.04 LTS)
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MYSQL
- Web server (Apache or Nginx): NGINX
- Manage mail accounts with iRedAdmin-Pro? not yet but plan to
- Related log if you're reporting an issue:
====

Hi,

Love this software. My question is: what is the most efficient way to find out how many mails each user has sent (per day/per week/per month).

Thanks in advance,

Marc Goldman