Recently a remote code execution bug came to light with Zimbra. It prompted me to update to the latest patch. I had some e-mail deliverability issues afterward. Here are my patch notes:

• Download the latest version from https://www.zimbra.com/try/zimbra-collaboration-open-source/
  • Follow instructions as listed here: https://wiki.zimbra.com/wiki/Zimbra_Releases/8.8.15/P32#Redhat
• Untar downloaded file, cd into directory and run ./install.sh as root
• Re-install latest patches (I had frustrating 500 errors until I discovered this was the fix)
  • sudo yum reinstall zimbra-patch
• Re-do any customization you’ve done to zimbra core
  • https://techblog.jeppson.org/2022/08/configure-zimbra-to-use-anymxrelay/
  • In my case, it was adding these lines to the smtp-amavis section:

    -o smtp_tls_security_level=none
    -o smtp_tls_wrappermode=no

• Restart Zimbra services
  • sudo -u zimbra zmcontrol restart