How is email forwarding handled by SMTP servers?

Email forwarding is a key function of SMTP (Simple Mail Transfer Protocol) servers, as it ensures that messages are properly directed to their intended recipients, even if they are on different servers or domains. SMTP servers handle this process by routing incoming emails based on specific server rules, which may include factors such as the recipient's address, server configurations, and any forwarding policies established by the server administrator.

When an email arrives at an SMTP server, the server will analyze the destination address and consult its routing tables to determine where to send the message next. This routing decision allows for efficient delivery across the internet, directing emails to the correct mail server that hosts the recipient's mailbox. This process not only ensures the swift delivery of emails but also allows for more complex forwarding setups, such as those involving multiple domains or when an address has been moved to a new server.

Options that involve marking emails for later delivery, deleting undeliverable emails, or sending notifications back to the sender do not accurately reflect the core functionality of email forwarding handled by SMTP servers. Instead, the primary mechanism of routing based on server rules is what enables effective communication and ensures that emails reach their intended recipients in a timely manner.