Philip Hazel wrote:
[...]
> [There was a later similar problem that showed up under Linux when Exim
> was being straced. This is fixed for 4.11, but unless you are stracing,
> it isn't relevant.]
Bingo! I straced Exim at the moment when this error occured but forgot
to mention this detail.
Now it's clearly reproducable using the same bounce procedure:
- no strace: Exim works well as expected
- strace -p PID -f: "remote delivery process count got out of step"
Many thanks for your quick answer!