E-Mail (SMTP) error codes

The classic SMTP error code consists of three digits (e.g. 220 mail.domain.tld SMTP ready.). The ESMTP status codes are additions to the classic code and consist of digits devided by dots (5.1.1 User unknown.). Many times you see both types of code combined (e.g. 550 5.1.1 User unknown). Find below a list of the most common codes:

2xx Request ok. Go ahead.

220 Mail service is running (ESMTP ready).

221 2.0.0 Closing connection (Mail received successfully, Goodbye).

250 2.0.0 Message accepted for delivery

250 2.1.0 Sender e-mail address ok.

250 2.1.5 Recipient e-mail address ok.

3xx Request ok, but more input is needed to complete the action successfully.

354 Enter mail, end with CRLF.CRLF

4xx Temporary error, try again.

421 4.2.1 The service is not available and the connection will be closed.

441 4.4.1 Cannot connect to remote host (host has DNS entry, but can’t be connected to).

450 4.5.0 Mailbox temporarily unavailable.

451 4.1.8 Sender e-mail address domain does not resolve temporarily.

451 4.7.1 Greylisting in action, please come back later.

454 4.7.0 TLS not available due to local problem. Please try again later.

5xx Permanent error. Don’t try again.

500 5.5.1 Syntax error, command unrecognized.

503 5.5.0 Sender e-mail address already specified.

503 5.5.1 Need MAIL before RCPT.

544 5.4.4 Host not found (not in DNS).

550 5.1.1 Mailbox does not exist.

550 5.1.3 Bad e-mail address syntax.

550 5.7.0 Your IP address is in a blacklist.

553 5.1.8 Sender e-mail address domain does not exist.

554 5.7.1 Relaying denied

14 thoughts on “E-Mail (SMTP) error codes”

  1. just trying to send mail with several photos & i get… smtp error [221] 2.0.0 bye
    what does this mean & how do i sort it? thanks

    1. [221] 2.0.0 bye is not an error. It is just confirming that you are ending the connection with the other mail server. Is that happening for all recipients?

  2. An internal CRM application that sends email now throws this message:

    Date : 3/24/2014 2:47:41 PM
    Description : Unable to connect to SMTP server.

    03/24/14 14:47:40 Opening Socket.
    Performing DNS lookup: smtpout.secureserver.net
    Connecting to:
    connection error: 0

  3. HI,
    Couls you please provide solution to error mentioned below :-
    The following recipient(s) cannot be reached:

    ‘Catherine Valenza’ on 2/26/2014 1:44 PM
    554 5.1.8 – Invalid email domain for:
    cvalenza at truenorthhealthcenter.org [R0109008]

    Sending address is a roadrunner email address.

  4. Having this same problem this morning and the Domain IS valid. We had it checked. For some reason when I send from my home email, it comes back with the 554 5.1.8 code.

  5. Could you please provide solution to overcome “5.1.8 Sender e-mail address domain does not exist.”

    Thanks in advance.

    1. This means that the domain of the sender address does not exist. There is no way to overcome this. You have to send from a valid domain (e.g. hotmail.com, gmail.com etc.).

  6. Please could you provide solution to “Server error: ‘451 4.7.1 Greylisting in action, please come back later”.

    Thanks and kind regards.

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