SMTP Protokolü - E-Posta Göndermek İçindir

Giriş
Açıklaması şöyle

An Internet e-mail message consists of two parts. We can refer to them as the envelope and the payload message or simply message.

The envelope has routing data: primarily, this is the sender address and one or more recipient addresses.

The message has the message content: subject line, message body, attachments, and so on. It also carries some technical information such as trace (Received:) headers, DKIM data, and so on; as well as the displayed sender and recipient addresses (what you see in the From, To and Cc fields in your mail client).

Here's the crux of it: The two don't have to agree!

SMTP sadece e-post göndermek içindir. E-Posta almak için IMAP veya POP protokolleri kullanılır. Açıklaması şöyle

What are IMAP and POP?

SMTP is an Internet Standard Communication Protocol for e-mail transmission. Similarly, reception of email involves two protocols: POP3 and IMAP.

Örnek
SMTP protokolü şuna benzer. Dolayısıyla elle telnet yaparak mail göndermek mümkün. İlginç bir şekilde istemci tek L ile HELO gönderir.

S: 220 smtp.server.com Simple Mail Transfer Service Ready
C: HELO client.example.com
S: 250 Hello client.example.com
C: MAIL FROM:<mail@samlogic.com>
S: 250 OK
C: RCPT TO:<john@mail.com>
S: 250 OK
C: DATA
S: 354 Send message content; end with .
C: 
C: .
S: 250 OK, message accepted for delivery: queued as 12345
C: QUIT
S: 221 Bye

Örnek - BCC

BCC iletişimi şöyledir.

HELO from-mail-server.com
MAIL FROM:<john.smith@from-mail-server.com>
RCPT TO:<anonymous@another-mail-server.com>
DATA
From: "John Smith" <john.smith@from-mail-server.com>
To: "Jane Doe" <jane.doe@to-mail-server.com>
BCC: "Anonymous" <anonymous@another-mail-server.com>
Subject: Important Meeting Notice
Date: Monday, May 15, 2017 12:20 PM

This is an important meeting notice. We'll meet tomorrow.

.

Sonuç Değeri
Açıklaması şöyle.

The protocol specs for SMTP in RFC 821 specifies the 550 return code that SMTP server should return when attempting to send an email to the incorrect address. But most of the public SMTP servers don’t do this. Instead, they send a “delivery failed” email to your box, or give no feedback at all.

For example, Gmail SMTP server sends a “delivery failed” message. And you get no exceptions in your program.