Email Magnifier
Online Test
Single Email Address Test
Bulk Email Address Test
Background Test
Email Address Test Task
Pricing
Help
Contact
Policy
What Is DNS
What Is SMTP
Our Test Algorithm
How To Use API
About
Sign In
About Email Magnifier email validation: learn about SMTP
SMTP
Simple Mail Transfer Protocol is a standard communication protocol for sending email messages.
Since the early 1980s it is one of the most used protocol types worldwide.
SMTP is used by email software mostly for sending mail, while the POP3 (Post Office Protocol 3) or the IMAP (Internet Message Access Protocol) for receiving mail.
All modern email client programs support SMTP.
The SMTP settings maintained in an email client include the IP address of an SMTP server (along with the addresses of either a POP or IMAP server for receiving emails).
ESMTP
Extended Simple Mail Transfer Protocol completes the original protocol for sending e-mail enabling to sent graphics, audio, and video files, and text in various national languages.
We use these commands when we verify email address
Connect
It's not actually a real command, but it is the first action we need to do it to start SMTP communication. There only two possible responses to this.
Code
Description
220
<domain> Service ready
421
<domain> Service not available, closing transmission channel
HELO
It is an alternative command to start the conversation, pointing that the server is using the ESMTP protocol. The responses are similar.
Code
Description
250
Requested mail action okay, completed
421
<domain> Service not available, closing transmission channel
500
Syntax error, command unrecognized
501
Syntax error in parameters or arguments
504
Command parameter not implemented
521
<domain> does not accept mail [rfc1846]
EHLO
An alternative command to start the conversation, underlying that the server is using the Extended SMTP protocol.
Code
Description
250
Requested mail action okay, completed
421
<domain> Service not available, closing transmission channel
500
Syntax error, command unrecognized
501
Syntax error in parameters or arguments
504
Command parameter not implemented
550
Not implemented
MAIL FROM
With this SMTP command the operations begin: the sender states the source email address in the “From” field and actually starts the email transfer.
Code
Description
250
Requested mail action okay, completed
421
<domain> Service not available, closing transmission channel
451
Requested action aborted: local error in processing
452
Requested action not taken: insufficient system storage
500
Syntax error, command unrecognized
501
Syntax error in parameters or arguments
552
Requested mail action aborted: exceeded storage allocation
RCPT TO
It identifies the recipient of the email, if there is more than one recipient, the command is simply repeated address by address.
Code
Description
250
Requested mail action okay, completed
251
User not local; will forward to <forward-path>
421
<domain> Service not available, closing transmission channel
450
Requested mail action not taken: mailbox unavailable
451
Requested action aborted: local error in processing
452
Requested action not taken: insufficient system storage
500
Syntax error, command unrecognized
501
Syntax error in parameters or arguments
503
Bad sequence of commands
521
<domain> does not accept mail [rfc1846]
550
Requested action not taken: mailbox unavailable
551
User not local; please try <forward-path>
552
Requested mail action aborted: exceeded storage allocation
553
Requested action not taken: mailbox name not allowed
QUIT
It terminates the SMTP conversation.
Code
Description
221
<domain> Service closing transmission channel
500
Syntax error, command unrecognized
Email Magnifier.
Copyright © All rights reserved.