Email sending refers to the process of transmitting digital messages from an origin point to one or more recipients over the internet. The mechanism is quite intricate and involves several stages and protocols to ensure that messages are sent and received correctly. Here’s a breakdown of the process:
1. Composing the Email:
- The sender creates a message using an email client, webmail service, or application. This involves specifying the recipient’s email address, subject line, body of the message, and attaching any necessary files.
2. Submission to Mail Server:
- Once the email is ready to be sent, the email client communicates with the server using a protocol, commonly SMTP (Simple Mail Transfer Protocol).
- The client authenticates with the SMTP server, usually with a username and password.
3. Routing the Email:
- The SMTP server processes the email, examining the recipient’s address.
- If the recipient’s domain (e.g., @example.com) is different from the sender’s domain, the SMTP server needs to relay the message to the recipient’s mail server.
4. Domain Name System (DNS) Lookup:
- To find out where to send the email, the SMTP server queries the DNS to retrieve the Mail Exchange (MX) records of the recipient’s domain.
- The MX record indicates the address of the recipient’s mail server.
5. Relaying the Email:
- The SMTP server establishes a connection to the recipient’s mail server.
- The recipient’s mail server may run various checks on the incoming email, including SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) to validate the email’s authenticity.
- Based on these checks, the recipient’s server decides whether to accept the email, reject it, or mark it as suspicious.
6. Storing and Retrieving the Email:
- Once accepted, the email is stored in the recipient’s mailbox on the server.
- The recipient then retrieves the email using an email client, which connects to the server using either IMAP (Internet Message Access Protocol) or POP3 (Post Office Protocol 3). IMAP keeps the email on the server, allowing multiple devices to access it, while POP3 typically downloads and removes it from the server.
7. Reading the Email:
- The recipient opens the email client or webmail interface and reads the email. Any embedded content, like images from external servers, might be fetched at this point, which can notify the sender that the email has been read (this is how read-receipts work).
8. Replying or Forwarding:
- The recipient can choose to reply to the email, forward it, archive it, delete it, or take other actions.
In conclusion, the email sending process involves various stages, from composition to reading. Along the way, several protocols and systems ensure the email is delivered accurately and securely. Given the potential for spam and malicious attacks via email, modern systems also incorporate multiple layers of validation and security checks.