Final answer:
To improve email deliverability, the best practices include using SPF and DKIM, which authenticate emails and prevent spoofing, whereas de-duplication, Spam Assassin, HTTPS, and SSL are not directly related to email deliverability.
Step-by-step explanation:
Improving Email Deliverability
The best practices that will improve your email deliverability are SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). These are email authentication methods that help prevent email spoofing by verifying that the sender of an email has permission to send emails from a domain. SPF allows the owner of a domain to specify which mail servers they use to send mail from that domain. DKIM provides an encryption key and digital signature that verifies that an email message was not faked or altered.
De-duplication is a process that involves removing duplicate records from a database and does not directly relate to the deliverability of emails, while Spam Assassin is a software tool that is used to detect and filter out spam emails, again not directly enhancing deliverability. HTTPS (Hypertext Transfer Protocol Secure) and SSL (Secure Sockets Layer) are protocols for securing online transactions and websites, but they are not directly related to email deliverability, although they could contribute to overall security practices.