[Evolution] Evolution doing a lot of network traffic to/from Exchange

[Paul Smith <paul mad-scientist net>]

Hi all;

Every so often I notice that there is a huge amount of network traffic
to/from my system, it can last for quite a while (hour+)

I started up nethogs and I can see that the traffic is between
Evolution and the Exchange server on my system, via port 443 (HTTPS) of
course.  I mean, things like 35 KB/sec upload and 90-110 KB/s download.

I'm not doing anything much with Evolution during this time, just
normal stuff, and I have "Check for new messages" set to 5 min.  Could
it be something with the GAL?  Or something else?

Is there any way to figure out what is going on here?

I'm using Evolution 3.46 (but I've seen this with 3.44 as well I'm
sure) from flatpak, running on Ubuntu 20.04 with Gnome 3.36.8 native.