Yes, that issue was solved in version 70. If that didn't happen, it's possible there were other issues that could have been investigated.
The support says that there were entries in Apache (/var/cpanel/templates/apache2_4/ea4_main.default) that should have been removed. He was referring to these lines:
So regardless of the status in Tweak Settings and Service Manager, did this file need to be edited manually?
No, that isn't the proper way to resolve the issue. cPanel will replace the template with as part of the nightly update. It might be time to just make a ticket with us.
It finally appeared to stop yesterday after I made below changes to ConfigServer (Firewall Configuration):
Thank you for your support.
Granted, this may happen again, but I did not receive single notification of "Excessive memory usage" notification overnight since yesterday. It was not mailman, but I later found out it was caused by Imunify360. I had tracked down to WebShield in Imunify360 that was causing a lot of memory usage, and actually it was causing hourly notification over the weekend (pointing to /usr/sbin/imunify360-webshield), but once I made above change to ConfigServer, it stopped finally.
Thank you for your support.