Is there any way to disable spam filter completely?

This work-around is impossible to set up.  First, "Sender's address" is not an option from the drop down of conditions.  Only "Sender contains" is in that list.  When attempting to use "Sender contains", along with the @ symbol to the right, the following error prevents one from saving the rule: "We can't save this rule because one or more of your free text inputs is invalid. Hint: make sure any text with a quote mark has a pair."

I have even tried putting the @ in quotes, such as "@" but this doesn't work either. 

VERY FRUSTRATING that this junk mail filter cannot be shut down or overridden by the user.  Another nail in Microsoft's coffin I guess.

Simply unbelievable there is still no option to just turn the SPAM filter completely off! Please Microsoft wake up! People are struggling with this. People invest time to write here and notify you about an obvious flaw in your email system. And you do nothing about it. This is so ignorant.

You should open a P1 ticket and assign it to the proper development team. Tell them to add a button in outlook.com to turn this SPAM filter completely off. PLEASE!

That doesn't work either. Maybe a simple on/off button for the spamfilter is easier? 

There's nothing to wait for. This has been going for over a year without even an acknowledgment.