==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 0.9.8 PRO:3.1 LDAP
- Linux/BSD distribution name and version: Debian 9.2
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): LDAP
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? Yes
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

I am running on a Google Cloud VM: 1 vCPU, 6 GB memory

Hello there! I have self taught myself basic linux and setting up a server over the past year. I am needing a little help in regards to where I can start in investigating this issue.

Like clockwork every 2-4 days our iredmail server becomes unresponsive (emails aren't processed and cannot access any web panels). It is easily fixed by shutting down and starting the server, everything begins working again. But after another few days...same problem.

With a preliminary investigation I have found that this issue correlates with the RAM usage on the VM. Right after a reset the RAM usage begins climbing...until a few days later it reaches 100% and then crashes. Once I restart the machine the RAM usage is lowered but begins its climb again. Attached is a screenshot of the VM's RAM usage over the past month or so (scroll down a bit to see the RAM usage)

My question is, where do I start to begin to investigating what is causing this issue? Or any ideas on what may be causing this? Any help would be greatly appreciated.