smsd: 3.1.21
Platform: Raspian, Linux <hostname> 4.9.35-v7+ #1014 SMP Fri Jun 30 14:47:43 BST 2017 armv7l GNU/Linux

If SMS comes in, the filename in eventhandler and the folder looks like /home/sms/spool/incoming_copy/smsserver.07aBp8

The filename in /home/sms/spool/incoming/smsserver.2017-08-21.zKVjqD had a different filename with the wanted date in it; but also a different extention. The filename in the incoming_copy-folder would not "renamed" after all. No difference between "normal SMS" and "REPORTs".

Sometimes, e.g. after complete processing a M2M-task, it is neccessary to handle both incoming files, e.g. for removing or archiving. No big deal, but you have alway open both files for searching message_id and phonenumber instead handle both files by filename.

smsd.conf
outgoing = /home/sms/spool/outgoing incoming = /home/sms/spool/incoming incoming_copy = /home/sms/spool/incoming_copy checked = /home/sms/spool/checked sent = /home/sms/spool/sent sent_copy = /home/sms/spool/sent_copy failed = /home/sms/spool/failed failed_copy = /home/sms/spool/failed_copy phonecalls = /home/sms/spool/phonecalls eventhandler_use_copy = yes date_filename = 2

Is there something I'v done wrong?

Names of files are meant to be unique, and therefore the extension is created based on the content of the target directory. Incoming_copy and other _copy directories are targeted to PlaySMS styled external applications, which read the file and then deletes it. Copy is used because in many cases smsd environment still needs old files, so deletion of main file is not acceptable.

It could be said that incoming is meant to humans, and incoming_copy is meant to M2M tasks.

If you need a copy with the same name, you should copy a file in your eventhandler instead of using built-in _copy feature.