In this guide, we will see how to read and analyze the different error returns following a malfunction in sending mail.
The main tool of any company is the mail service. In order to ensure maximum efficiency and compatibility, it is necessary to constantly update this tool which is more or less complex. To use the mail service, you have to use a mail program or directly via webmail. In this context, errors occur from time to time, and vary from one tool to another.
First, we will mention some common mistakes and the steps to follow to solve them.
| Error code | Explanation |
What to do? |
| 101 | The server is unable to connect. | The server name may be misspelled. It must be corrected. If the server is correct, in this case check or change the connection port. |
| 111 | The connection is refused, or impossible to open an SMTP session. | This is usually a problem with the remote connection to the SMTP server, caused by a block in the firewall, or misspelled domains. It is necessary to check all the configurations or to ask for assistance from the Internet service provider. |
|
211 |
System status or help response. | Nothing to do in this case. The e-mail sent is well delivered and the return gives more information about the server. |
| 214 | This is a response to the HELP command. | Nothing to do in this case. The email sent is delivered and the return email gives more information about the server and it redirects to a FAQ page. |
| 220 | The server is ready. | Nothing to do in this case. The e-mail sent is well delivered and the return gives a welcome message. |
| 221 | The server closes its transmission channel. The sent e-mail can be delivered with messages like "Goodbye" or "Closing connection". | Nothing to do in this case. The e-mail sent is delivered and the return message indicates that the e-mail session has ended. |
| 250 | The server has successfully transmitted the message. "Requested mail action okay completed". | Nothing to do in this case. The e-mail sent is delivered. |
| 251 | The recipient's account is not present on the server, and the e-mail sent will be relayed to another server. "User not local will forward" | Nothing to do in this case. The e-mail sent is delivered. This is a normal forwarding action. That is, the recipient's address forwards the e-mail to another e-mail address. |
| 252 | The server can't verify the user, but it will try to forward the sent email anyway. | Nothing to do in this case. The sent e-mail is delivered. The e-mail address of the recipient is valid, but it is not possible to verify it. Usually, the server transfers the message to another server that will be able to verify it. |
| 354 | The message can be very cryptic ("Start mail input end ."). This is the typical response to the DATA command issued in terminal following the use of the TELNET command. | Nothing to do in this case. The server has received the "From" and "To" details of the email, and is ready to pass the message body. |
| 420 | There were problems with the transfer of messages. "Timeout connection problem": | Try sending the email again later. This is usually a problem with the recipient's firewall. |
| 421 | The service is unavailable due to a connection problem. It may refer to exceeding the limit of simultaneous connections, or to a more general temporary problem. | Nothing to do in this case. The server (of the sender or the receiver) is not available at the moment. The system will try to resend it later. |
| 422 | The recipient's box has exceeded its storage limit. | You must contact the recipient by another means (via a different email address, by phone, or via a form on their site, etc.) to alert them and ask them to create free space on their box. |
| 431 | Not enough space on the disk, or an "out of memory" due to a file system overload. | Try dividing the list of recipients into several smaller lists and resending the email. |
| 432 | This is the Microsoft Exchange SMTP error code. "The recipient's Exchange Server incoming mail queue has been stopped". | The recipient must be contacted by another means (via a different email address, by phone, or via a form on his site, etc.) to alert him. GeGenerally, this is due to a connection problem. |
| 441 | The recipient's server does not respond. | Nothing to do in this case. There is a problem with the user's incoming server. The system will try to contact him again automatically. |
| 442 | The connection was interrupted during transmission. | A typical network connection problem, due to your router. You should check your connection immediately, then try to resend the email. |
| 446 | "The maximum hop count was exceeded for the message: an internal loop has occurred". | You must contact our assistance if you use our outgoing SMTP server. |
| 447 | The session to send the email has expired due to problems with the recipient's incoming server. | This usually happens when the sending limits are exceeded. Try dividing the list of recipients into several smaller lists and resending the email. |
| 449 | A routing error. | Like the 432 error, it is only related to Microsoft Exchange. |
| 450 | The mailbox has been corrupted or placed on an inaccessible server, or your email address has not been accepted due to IP or blacklisting problems. "Requested action not taken - The user's mailbox is unavailable". | Nothing to do in this case. The server will try to send the e-mail again, after some time. You can check if the sending server is not blacklisted. |
| 451 | A temporary error that means that it is impossible to connect to the sending server. "Requested action aborted - Local error in processing". | If the error keeps recurring, contact our assistance if you use our outgoing SMTP server. |
| 452 | Too many emails sent or too many recipients. This indicates an overuse of resources. | Nothing to do in this case. The next attempt usually succeeds. If there is a problem, the sent e-mail will be rejected with the message "Out of memory". |
| 471 | An error on your mail server, often due to a local spam filter problem. | You must contact our assistance if you use our outgoing SMTP server. |
| 500 | A syntax error in the command launched in terminal. | It is a bad interaction between the server and your firewall or antivirus. Check carefully the instructions to solve it. |
| 501 | A syntax error in the parameters or arguments of the command launched in terminal. | In most cases, this is due to an invalid e-mail address, but it can also be associated with connection problems, or a problem with your antivirus settings. |
| 502 | The command is not implemented. The command has not yet been activated on your own SMTP sending server. | Contact your supplier for more information. |
| 503 | The server has encountered a wrong command sequence, or it requires authentication. | In case of a "bad sequence", the server has withdrawn its orders in the wrong order, usually due to a connection failure. If authentication is required, you must insert your username and password. |
| 504 | The command is not implemented. | A syntax error; contact your supplier. |
| 510/511 | "Bad email address". | One of the addresses in your A, CC or CCI line does not exist. Check again and correct any possible spelling mistakes. |
| 512 | A DNS error: the host server for the recipient's domain name cannot be found. | Check all your recipients' addresses again: there will probably be an error in a domain name (like mail@domain.coom instead of mail@domain.com). |
| 513 | "Address type is incorrect": another problem with writing addresses. In some cases, however, it is related to an authentication problem. | Check the addresses of your recipients and correct any errors. If everything is OK and the error persists, it is caused by a configuration problem (simply, the server needs authentication). |
| 523 | The total weight of your shipments exceeds the limits of the server recipient. | Resend your message by dividing the list into smaller subsets. |
| 530 | Normally, an authentication problem. But sometimes the recipient's server is blacklisting yours, or there is an invalid email address. | Configure your settings by providing a username and password authentication. If the error persists, check all your recipients' addresses and whether you have been blacklisted. |
| 541 | The recipient's address has rejected your message: normally, this is an error caused by a spam filter. | Your message has been detected and identified as spam. You must ask the recipient to whitelist you. |
| 550 | It usually sets a non-existent email address on the remote side. | Although it can also be returned by the recipient's firewall (or when the incoming server is down), the vast majority of 550 errors simply say that the recipient's email address does not exist. You need to contact the recipient in another way and get the correct address. |
| 551 | "User not local or invalid address - Relay denied". If either your address or the recipient's address are not locally hosted by the server, a relay may be interrupted. | This is a (more or less clever) strategy to avoid spamming. You should contact your ISP and ask them to label you as an authorized sender. |
| 552 | "Requested mail actions aborted - Exceeded storage allocation": quite simply, the recipient's mailbox has exceeded its limits. | Try to send a lighter message: this error usually happens when you send emails with large attachments. |
| 553 | "Requested action not taken - Mailbox name invalid". In other words, there is an invalid email address in the recipients line. | Check all addresses in the TO, CC and CCI fields. There should be an error or misspelling somewhere. |
| 554 | This means that the operation has failed. This is a permanent error and the server will not try to send the message again. |
Usually the incoming server thinks your email is spam or the sending IP address is blacklisted. Check carefully if the IP is in some spam lists. |
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