I had this same problem. I followed did like rpuakg said and uninstalled the gmail smtp plugin and it fixed me up.
Hi All,
I had the exact same problem. It seems that any plugin that is related to email can cause this issue. In my case, it was the “ShiftThis.net | Swift SMTP 1.0 Send email via SMTP (Compatible with GMAIL) By Marcus Vanstone” plugin. As soon as I deactivated the plugin, my comments started to get approved and I also started to receive emails when comments were posted.
Hope it helps someone.
