Hello,
> If you haven't set maildir_use_size_file, Exim just adds up the sizes of
> all the files in the directory, recursively. At least, that's what it is
> supposed to do. Running a test with -d-all+transport will show what it
> is *actually* doing.
now it is getting clear what is causing the quota exceeding:
Our maildirs are limited to 100 MB and exim is enforcing this. But if a
mail is detected to be spam, then we put it into the Junk-folder of the
user, which means that for exim the .Junk-folder within the base-Maildir
(exim cannot know that this is the base Maildir) is the Maildir and it
is only adding the sizes of files within this .Junk-folder. So that way
a Maildir could get a size up to 200 MB.