From: professor@university.edu
To: student@university.edu
Subject: Lecture notes - Introduction to Computer Networks
Date: Thu, 23 Jan 2025 16:45:00 +0100
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Message-ID: <lecture-notes-001@university.edu>

Dear Student,

Here are the key points from today's lecture on SMTP:

1. SMTP uses TCP port 25 (or 587 for submission)

2. Basic commands:
   - HELO/EHLO: Client identifies itself
   - MAIL FROM: Specifies the sender
   - RCPT TO: Specifies the recipient(s)
   - DATA: Begins the message content
   - QUIT: Ends the session

3. Response codes:
   - 2xx: Success
   - 3xx: Intermediate (e.g., 354 for DATA)
   - 4xx: Temporary failure
   - 5xx: Permanent failure

4. The message body ends with a line containing only "."

Please review RFC 5321 for more details.

Best regards,
Prof. Network
