The maillogger is a ZServer related functionality that is no longer available with Plone 5.2 running under WSGI.
What would be a suitable replacement (apart from external services like Sentry)?
mailinglogger is a standalone library (https://pypi.org/project/mailinglogger/) providing handlers for the standard Python logging framework, and most WSGI servers either don't interfere with Python logging or provide a way to configure it. It shouldn't be too difficult to put the pieces together.
I use tha.logcheck for my Plone4, a bit out dated, but still usable.
There is a write-up at https://reinout.vanrees.org/weblog/2009/03/31/logchecker-zope-logfiles.html
No more in pypi, but can get it at
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