Firstly, is important to mention that this lowering in speed was noted after emergency security update for Internet Explorer on September 23. IERenderer used to be much faster in the past and the only event I can remember was that patch. https://www.ghacks.net/2019/09/24/microsoft-releases-emergency-internet-explorer-security-update
I don't use IE so I can't say the browser was also affected. What is noticed is that anytime I open a message with remote graphics Pmail seems to hang and the hourglass is shown for several seconds. I usually swap to another task window returning after a while when the message is made available. Changing the renderer to BearHTML make the mail opening almost instant.
Any thoughts?