How to check if the mail has been sent successfully

Question

I am developing an Asp.Net application, where I am sending a mail to the user\'s email address, if he forgets the password.

I want to check if the mail has been sent

Answer 1

According to spec:

S: 220 smtp.example.com ESMTP Postfix
C: HELO relay.example.org
S: 250 Hello relay.example.org, I am glad to meet you
C: MAIL FROM:<bob@example.org>
S: 250 Ok
C: RCPT TO:<alice@example.com>
S: 250 Ok
C: RCPT TO:<theboss@example.com>
S: 250 Ok
C: DATA
S: 354 End data with <CR><LF>.<CR><LF>
C: From: "Bob Example" <bob@example.org>
C: To: Alice Example <alice@example.com>
C: Cc: theboss@example.com
C: Date: Tue, 15 Jan 2008 16:02:43 -0500
C: Subject: Test message
C:
C: Hello Alice.
C: This is a test message with 5 header fields and 4 lines in the message body.
C: Your friend,
C: Bob
C: .
S: 250 Ok: queued as 12345
C: QUIT
S: 221 Bye
{The server closes the connection}

As soon as server says 250 Ok: queued as 12345, you cannot know for sure if it had really sent an email or not, or whether it was delivered.

Answer 2

No. E-mail (SMPT based) is an unreliable transport protocol and although there are some hacks to detect that an e-mail has been received and read, e.g. by embedding an individualized image URL in the e-mail and tracking that the image has been requested by the recipient's client, there is no absolutely reliable way to fulfil your request.