SPF cause my mail to be rejected code example

Example: SPF cause my mail to be rejected

Type their domain in to this tool (an SPF record checker) and see if it passes.
http://mxtoolbox.com/spf.aspx
http://www.kitterman.com/spf/validate.html

The solution that worked for me is adding DNS TXT record.
TYPE 		NAME(YOUR DOMIAN) 					VALUE						   TTL
TXT sydneysideloaders.com.au "v=spf1 include:spf.protection.outlook.com -all" 3600

If no problem found, the problem is on their end. an invalid SPF record means it
could be spam / or a forged address and it seems reasonable to me to reject such
messages.

TLDR It's their problem, tell them to fix their SPF record. The alternative 
makes YOU less secure.