This could be a nasty one. The crash occurs after the data structure of the mail
was unloaded in outlook and GpgOL already completely detached it's event
handlers from the object and frees up the memory. GpgOL is not executing any
code when the crash occurs. That outlook blames GpgOL is likely because it jumps
into an invalid memory region that was allocated for GpgOL but is no longer
valid. This shouldn't happen though as we have already successfully unregistered
all our callbacks.
So I currently think that somehow when using send from explorer outlook through
some side effect / bug does a callback into GpgOL's event handling code which
was already destroyed. I'll try to confirm that theory on monday by keeping the
event handlers around after the unload event occurred.
Also does not appear that we are the first ones with that problem:
https://forum.kaspersky.com/index.php?showtopic=225375
:-/