SPF and DKIM is configured for your domains so the message you send have that protections enabled. But for received messages, DKIM or SPF is not enforced meaning the server accept all message including those that fails on any or both of this categories.
It might be a nice improvement to set this check as an option I think. I receive spoofing messages and lots of spam, so I think this can at least improve a bit the situation.
If it is not going to be an option, should I proceed on my own enabling this for postfix following standard ubuntu+postfix guidelines or may you suggest any procedure for that?