Target mail servers do not check for SSL and not for SMTP authentication. Because these things can only be checked at the first mail server in the delivery chain. So all information in the header about SSL and authentication could be forged along the way. Target servers can only check the server they actually accept the mail from. These servers are checking for 1,2,3 and 6.
Additionally they check the HELO name, Blacklists and Whitelists. Very good servers also check the reputation. Meaning they check the historical rate between ham and spam of an IP address. Some also take into account from which country the mail originates and if the language matches. Others do fuzzy checksumming and calculate the amount of mails with the same checksum.
There are far more points checked. The SpamAssassin ruleset consists of hundreds of rules that all are taken into account. Some postmasters even have their own rules that block Spam.
Spam blocking is way too localized. While you can safely reach one recipient's mailserver, another recipient's will probably block the mail (even with the same content).