There’s nothing special with CIFS or other network shares, but there are many many limitations with the type of user mode secure delete AxCrypt (and most similar utilities) use.
What we do, is simple overwrite the file with random data. If the file system “at the other end” for example is journalling and retains shadow or generational copies, this are still there. If the file system or underlying firmware, for some reason does not actually write the actual data of the original file (for example SSD disks), or detects that the file is deleted soon afterwards the caching mechanism could determine the writes are “unnecessary”.
AxCrypt secure wipe protects against standard recovery measures, but not necessarily against advanced forensic techniques. For that physical destruction is the only known method guaranteed to work.