Mail server lookup

My "send from" domain is unbeatablesale.com.  The mail server domain
is pmx1.unbeatablesale.biz.

It appears some receiving smtp servers, microsoft, very few, require
the txt spf record of the sending mail server.  Is this correct spf
implementation?  If yes, do all mainstream mail providers that have
spf checking check for mail server's spf txt record?  The reason why I
am asking is that I would rather put spf record on the outbound mail
server, ie pmx1.unbeatablesale.biz, rather than on "send from" domain
unbeatablesale.com.

Thanks in advance