{"id":73,"date":"2022-09-01T00:01:04","date_gmt":"2022-09-01T05:01:04","guid":{"rendered":"http:\/\/www.maxprog.com\/blog\/?p=3"},"modified":"2026-02-25T12:47:11","modified_gmt":"2026-02-25T17:47:11","slug":"how-to-understand-the-smtp-server-response-codes","status":"publish","type":"post","link":"https:\/\/www.maxprog.com\/blog\/how-to-understand-the-smtp-server-response-codes\/","title":{"rendered":"How to understand the SMTP Server Response Codes"},"content":{"rendered":"

How to understand the SMTP Server Response Codes? Well, it comes out that all the SMTP Server Response Codes are standard. In other words, SMTP servers always respond to requests\/commands using the very same defined set of codes. The SMTP Server Response Codes are part of the SMTP protocol<\/a>, the set of rules used to send emails.<\/p>\n

As a reminder, an SMTP server is the type of server you use to send emails. SMTP is also the name of the protocol that defines the delivery of emails over the internet. Sending a message actually consists of connecting to an SMTP server, sending commands, and collecting responses.<\/p>\n

In the MaxBulk Mailer ‘Delivery’ panel you will see those commands and responses. Most of the time the server also adds a tiny description of the response codes:<\/p>\n

\"SMTP<\/p>\n

MaxBulk Mailer reads and handles all those responses automatically. It will also display human-readable notifications, warnings, and errors. However, it can be useful to know about those SMTP Server Response Codes in order to troubleshoot small issues yourself, especially connection and authentication problems.<\/p>\n

This post is a small guide to the codes mail servers may produce when you try to send mail along with their meanings.<\/p>\n

Note that if the SMTP server doesn’t connect or doesn’t respond to MaxBulk Mailer commands you will get a time-out error. You will not get any SMTP Server Response Codes. In such a case, you will have to check your server address, the server port, and the SSL settings.<\/p>\n

How to understand the SMTP Server Response Codes<\/h3>\n
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So, as said above, any mail server will reply to every request\/command a mail software such as MaxBulk Mailer<\/a> makes with a return code. This code consists of three digits.<\/p>\n

The first digit generally tells whether the server accepted the command and if it could handle it. The five possible values are:<\/p>\n

1:<\/strong> The server has accepted the command, but does not yet take action.
\n2:<\/strong> The server has completed the task successfully.
\n3:<\/strong> The server requires further information to complete the request.
\n4:<\/strong> The server has encountered a temporary failure.
\n5:<\/strong> The server has encountered an error.<\/p>\n

The second number gives more information. Its six possible values are:<\/p>\n

0:<\/strong> A syntax error has occurred.
\n1:<\/strong> Indicates an informational reply, for example, to a HELP request.
\n2:<\/strong> Refers to the connection status.
\n3<\/strong> and 4<\/strong> are unspecified.
\n5:<\/strong> Refers to the status of the mail system as a whole and the mail server in particular.<\/p>\n

The last number is even more specific and shows more graduations of the mail transfer status.<\/p>\n

There are many pages with detailed explanations of all those codes. You can visit our page The Meaning of the SMTP response Codes<\/a>, the Wikipedia page<\/a> or do a Google search<\/a>. I personally recommend this page<\/a>.<\/p>\n

Video-Tutorial<\/h3>\n
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