|IP Reputation||Several services on the Internet track reputation of IP addresses through Real-time Blackhole List (RBL) servers.|
|SPF, DKIM & DMARC||Most filtering solutions will use these technologies to filter forgeries.|
|Dynamic IP addresses||Email servers are meant to run on networks with static IP address. Email filtering software will reject emails generating from dynamic IP addresses|
|Network best practices||It is expected that the sending server follow certain best practices, such as having MX and PTR record in the DNS server. Additionally, using SSL/TLS when communicating is also becoming popular.|
*.rtffiles disguised as a
*.zipfile containing harmful attachments, such as a document that say "Invoice.xlsx"