Receiving an email involves a series of steps that ensure the message sent by the originator is accurately and securely delivered to the intended recipient. Here’s a breakdown of the email receiving process:
1. Email Transmission:
- The sender’s email client submits the composed email to the sender’s SMTP (Simple Mail Transfer Protocol) server for transmission.
- If the recipient’s domain (e.g., @example.com) is different from the sender’s domain, the SMTP server relays the message to the recipient’s mail server.
2. Domain Name System (DNS) Lookup:
- The sender’s SMTP server queries the DNS to retrieve the Mail Exchange (MX) records of the recipient’s domain to identify the appropriate receiving mail server’s address.
3. Reception by the Mail Server:
- The SMTP server establishes a connection to the recipient’s mail server.
- The recipient’s mail server may then run various checks on the incoming email, including:
- SPF (Sender Policy Framework): Verifies if the email originates from a valid server for the sender’s domain.
- DKIM (DomainKeys Identified Mail): Checks if the email’s content was altered during transit.
- DMARC (Domain-based Message Authentication, Reporting & Conformance): Provides a method for the sender to indicate that their emails are protected by SPF and/or DKIM, and tells the recipient’s server what to do if the checks fail.
4. Decision Based on Authenticity Checks:
- Depending on the results of the SPF, DKIM, and DMARC checks, the recipient’s server can:
- Accept the email.
- Mark it as suspicious or spam.
- Reject and not deliver it.
5. Email Delivery to the Mailbox:
- Once the email passes the security checks, it’s stored in the recipient’s mailbox on the server, awaiting retrieval.
6. Retrieval by the Email Client:
- The recipient’s email client periodically checks the mail server for new emails.
- When a new email is detected, the email client retrieves it using either IMAP (Internet Message Access Protocol) or POP3 (Post Office Protocol 3). IMAP synchronizes emails between the server and multiple devices, allowing the email to be accessed from anywhere. In contrast, POP3 typically downloads the email to a single device, removing it from the server.
7. Reading the Email:
- The recipient can now read the email using their email client or webmail interface.
- Actions like opening attachments, clicking on links, or loading external images might be tracked by the sender, depending on the email’s content and the settings in the recipient’s email client.
8. User Actions:
- After reading, the recipient can choose to reply, forward, delete, archive, or move the email to a specific folder, among other actions.
In conclusion, the email receiving process, like the sending process, is multifaceted. It’s designed to ensure that messages are accurately delivered to the intended recipient while also incorporating security measures to protect against spam, phishing, and other malicious activities.