Home Products Downloads News Store Support

SMTP Server Response Codes | MaxBulk Mailer ▸ Frequently Asked Questions

SMTP Server Response Codes

MaxBulk Mailer ▸ Frequently Asked Questions

Compatible with MS Windows Compatible with MacOS

SMTP Server Response Codes

SMTP servers use to respond to commands using a defined set of codes. This page is a small guide to the codes mail servers may produce when you try to send mail along with their meanings. They are part of the SMTP protocol (the set of rules used to send emails).

SMTP client server connection
The Meaning of the Codes
A mail server will reply to every request a client (such as MaxBulk Mailer) makes with a return code. This code consists of three numbers.

New paragraph The first generally tells whether the server accepted the command and if it could handle it. The five possible values are:

1: The server has accepted the command, but does not yet take action. A confirmation message is required.

2: The server has completed the task successfully.

3: The server has understood the request, but requires further information to complete it.

4: The server has encountered a temporary failure. If the command is repeated without any change, it might be completed.

5: The server has encountered an error.

New paragraph The second number gives more information. Its six possible values are:

0: A syntax error has occured.

1: Indicates a informational reply, for example to a HELP request.

2: Refers to the connection status.

3 and 4 are unspecified.

5: Refers to the status of the mail system as a whole and the mail server in particular.

New paragraph The last number is even more specific and shows more graduations of the mail transfer status.

This leads us to the detailed list of ESMTP server response codes, as layed down in RFC 821 and later extensions.

Code Description
211 System status, or system help reply.
214 Help message (for a human reader follows).
220 SMTP Service ready (or Ready to start TLS).
221 SMTP Service closing transmission channel.
250 OK, queuing for node node started. Requested mail action okay, completed (Requested action taken and completed).
251 OK, no messages waiting for node node. User not local, will forward to forwardpath (The recipient is not local to the server, but the server will accept and forward the message).
252 Cannot VRFY user (e.g., info is not local), but will take message for this user and attempt delivery (The recipient cannot be verified, but the server accepts the message and to attempt delivery).
253 OK, messages pending messages for node node started.
354 Start mail input; end with <CRLF>.<CRLF>. This indicates that the server is ready to accept the message itself (after you have told the server who the message is from and who you want it to be sent to).
355 Octet-offset is the transaction offset.
421 Domain service not available, closing transmission channel (The service is not available and the connection will be closed).
432 A password transition is needed.
450 Requested mail action not taken: mailbox unavailable.
ATRN request refused (The requested command failed because the user's mailbox was unavailable, for example because it was locked).
451 Requested action aborted: local error in processing. Unable to process ATRN request now (The command has been aborted due to a server error. Not your fault. Maybe let the admin know).
452 Requested action not taken: insufficient system storage (The command has been aborted because the server has insufficient system storage, it happens sometimes when sending to a lot of recipients in Bcc mode).
453 You have no mail.
454 TLS not available due to temporary reason.
Encryption required for requested authentication mechanism.
458 Unable to queue messages for node node.
459 Node node not allowed: reason.
500 Command not recognized: command. Syntax error (The server could not recognize the command due to a syntax error).
501 Syntax error, no parameters allowed (A syntax error was encountered in command arguments).
502 Command not implemented (This command is not implemented).
503 Bad sequence of commands (The server has encountered a bad sequence of commands).
504 Command parameter not implemented (A command parameter is not implemented).
505 Authentication required
521 Machine does not accept mail.
530 Must issue a STARTTLS command first.
Encryption required for requested authentication mechanism.
534 Authentication mechanism is too weak.
538 Encryption required for requested authentication mechanism.
550 Requested action not taken: mailbox unavailable (The requested command failed because the user's mailbox was unavailable, for example because it was not found, or because the command was rejected for policy reasons).
551 User not local; please try forwardpath (The recipient is not local to the server. The server then gives a forward address to try).
552 Requested mail action aborted: exceeded storage allocation (The action was aborted due to exceeded storage allocation).
553 Requested action not taken: mailbox name not allowed (The command was aborted because the mailbox name is invalid).
554 Transaction failed.
571 No external routing allowed, remote sending only allowed with authentication (Illegal relay, missing authentication, RBL/blacklisting)
572 Bounces are blocked due to system abuse by spammers

 ▸ Blue rows correspond to successfull responses.
 ▸ Rose rows correspond to delivery errors
 ▸ Red rows corresppond to server errors.

Recent questions from our MaxBulk Mailer users
  451 Error code NEW Screenshot
  Problem sending email to Gmail recipients UPDATED Screenshot
  What is the meaning of the recipient panel icons UPDATED Screenshot
  What is the best mail server I can use with MaxBulk Mailer Screenshot
  How can I export my lists to a new computer Screenshot
  How to send a HTML email Screenshot
  How to hide text in my message Screenshot
  Google ending support for less secure apps YouTube Video
  How to add social networks icons to my message Screenshot
  How do I set up an unsubscribe link Screenshot
  How to export several lists into to a single file Screenshot
  What are the Zoho mail settings for MaxBulk Mailer? Screenshot
  Emails sent but not received Screenshot
  HTML Email is received empty Screenshot
  How to use an alternative text when a tag value is empty Screenshot

MaxBulk Mailer is a full-featured and easy-to-use bulk mailer and mail-merge software for macOS and Windows that allows you to send out customized press releases, prices lists, newsletters and any kind of text or HTML documents to your customers or contacts.

MaxBulk Mailer is fast, fully customizable and very easy to use. MaxBulk Mailer handles plain text, HTML and rich text documents and gives full support for attachments. With MaxBulk Mailer you will create, manage and send your own powerful, personalized marketing message to your customers and potential customers.

Thanks to its advanced mail-merge and conditional functions you can send highly customized messages and get the best results of your campaigns. You also have support for international characters, a straightforward account manager with support for all type of authentication schemes including SSL, a complete and versatile list manager, support for importation from a wide range of sources including from remote mySQL and postgreSQL databases.

MaxBulk Mailer is a software tool that you purchase once, no need to pay on a per-email basis to submission services!

▾ Last videos, Online events and Q&A Sessions ▾
▾ Last customer reviews ▾

🔐 Secured by Sectigo SSL | UptimeRobot - Site Loaded properly