Smtp ошибка 551

Email Error 551 is an SMTP error commonly seen in MailEnable servers, and is seen in two forms:

551 Sender address is not valid for your login

and

551 This mail server requires authentication before sending mail from a locally hosted domain

MailEnable is widely used in Plesk web hosting servers, and these errors are often reported to web hosting providers. As part of our Outsourced Web Hosting Support services, we use multiple strategies to resolve Error 551.

But before we get into the details, let’s see what this error means:

What is SMTP Email Error 551?

In SMTP protocol, Error 551 is shown when a sender is not found to be authorized to relay mail through the server. This is a strategy to combat spam. It can be implemented in two forms:

1. Sender or Recipient mail address not authorized

For an SMTP server to accept a mail into the queue, either the Sender’s Mail Address or the Recipient’s Mail Address should be hosted in the SMTP server.

In MailEnable servers, this is controlled by a setting called “Authenticated senders must use valid sender address“.

[ Use your time to build your business. We’ll take care of your customers. Hire Our Hosting Support Specialists at $10.94/hr. ]

2. Sender not authenticated

A mail is accepted by the server only if the sender is authenticated using a password.

In MailEnable servers, the setting “Senders from local domains must authenticate to send email” is used to enable this feature.

RELATED : How to fix email error “554 5.7.1 : Relay access denied”

How to fix Error 551 in MailEnable servers

Mail sending through SMTP authentication is a powerful way to block spammers. So, we recommend web hosting providers to keep the setting “Senders from local domains must authenticate to send email” enabled at all times.

However, the setting “Authenticated senders must use valid sender address” is seen to cause more harm than good. So, for servers in which Error 551 is common, we recommend disabling this option.

It can be done by going to SMTP Properties >> Security tab.

[ Running a hosting business doesn’t have to be hard, or costly. Get world class Hosting Support Specialists at $10.94/hour (bulk discounts available) ]

Fixing Error 551 in mail clients like Outlook, Thunderbird, Eudora, etc.

Some web hosts value the additional security of the default MailEnable settings. In those cases, we (as the web host’s support team) help web masters configure their mail clients.

Here’s how:

1. How to fix “551 Sender address is not valid for your login”

This error is returned by the mail server while sending mail, and is displayed by in email clients such as Outlook Express.

This error is caused by an anti-spoofing feature in MailEnable servers, which can be set by enabling “Authenticated senders must use valid sender address” in order to prevent spoofing.

The best solution is to disable this setting in MailEnable. However, if it cannot be done, mail client settings need to be reviewed. Here’s how:

Verify the login details of the email account configured in the email client and confirm that it matches the actual email account.

For instance, if your email account is bob@bobcares.com, then it should be specified in the logon information and all the e-mail address fields in Outlook.

2. How to fix “551 This mail server requires authentication before sending mail from a locally hosted domain”

This is another error 551 that happens when you try to send email from the email client using MailEnable email server, without properly authenticating it.

The error message shown in the email client, say Outlook, would be as:

The server rejected the sender address. The server response was: 551 This mail server requires authentication before sending mail from a locally hosted domain. Please reconfigure your mail client to authenticate before sending mail.

This error 551 occurs when “SMTP authentication” is not enabled in your email client. The solution is to configure your mail client to use SMTP authentication.

In Outlook, the option ‘My server requires authentication‘ in the ‘Outgoing Server‘ section should be checked to enable authentication.

Before sending email, authenticate the account by providing the mail account username and password.

There are two other workarounds for this error in the MailEnable server, which are not commonly recommended due to security reasons:

1. This 551 error occurs because MailEnable security feature doesn’t permit spoofing. Disabling this security feature by selecting the option: “Anyone can spoof sender addresses“, will prevent this error.
2. Another workaround is to allow relaying for trusted IP addresses. The setting “Allow relay for privileged IP ranges” in MailEnable can be used to permit relaying for certain IP addresses and to prevent such error messages.

The 551 error message ‘This mail server requires authentication before sending mail from a locally hosted domain‘ has many variants:

1. 551 User not local or invalid address – Relay denied.
2. 551 Relay request denied
3. 551 This is not a relay host
4. 551 Authentication required for relay
5. 551 User not local; please try

We’ve been able to prevent server incidents by up to 15% by using our proactive server checks (click here to see how we improve web hosting support).

Other reasons for Email Error 551

Today we’ve seen the two major 551 errors in MailEnable and the fixes for that. But there maybe cases like mailbox records missing or email client setting errors, that cause the error.

Another common error 551 is “551 Mailhost is on our global blacklist” or “551 Sender is on domain’s block list“. This happens when the recipient mail server bounces email from the sender, which is in its blacklist.

551 email errors can happen in a variety of ways. Messages such as “551 No valid recipients“, “551 not our customer“, “551 Unknown user“, “551 user does not exist“, etc. shows that the recipient email address does not exist in the mail server.

The settings to fix may vary based on the email client used. Outlook Express, Thunderbird, Eudora, Microsoft Outlook, etc. are some of the commonly used email clients by our customers.

Bobcares provides Outsourced Hosting Support and Outsourced Server Management for online businesses. Our services include Hosting Support Services, server support, help desk support, live chat support and phone support.

What’s Causing This Error

SMTP error 551 occurs when an email bounces during the delivery process. Two types of bounces may take place:

1. Soft Bounce — Soft bounce takes place when the recipient’s mailbox is full or if their email server is temporarily unavailable
2. Hard Bounce — Hard bounce occurs when the email address is invalid or if the mail server attempts to deliver the email to another server that does not handle the recipient’s email address.

The reason behind this error code may not always be clear and other reasons can also contribute to causing an email to bounce.

Solution — Here’s How To Resolve It

To resolve this error, ensure no underlying issues affect the email server or the connectivity.

The following common troubleshooting steps can help narrow down and resolve the issue at hand:

1. Ensure that all recipient’s email addresses are valid.
2. Ensure that the recipient has enough space in their mailbox to receive the email.
3. Ensure that the recipient’s email server is available and is accepting email.

A 551 email error is normally ecountered when there is an attempted delivery to a mail server that doesn’t handle mail for the specified recipient.

You should receive a bounce-back message from the server with a variation of email error 551 in the subject, and the body should contain your original message that you attempted to deliver.

Example bounce-back message

Common variations of the 551 email error

• 551 5.1.1 recipient is not exist
• 551 5.1.1 user does not exist
• 551 Denied IVF
• 551 not our customer
• 551 [email protected] failed to route the address
• 551 <[email protected]>… User not locali
• 551 Relay request denied
• 551 This is not a relay host – mail must be to or from host domain.
• 551 Unknown user.
• 551 User not local. Authentication required for relay
• 551 User not local; please try <forward-path>

Resolving a 551 email error bounceback

What is SMTP?

SMTP stands for Simple Mail Transfer Protocol. This document provides the brief explanation about SMTP reply codes.

SMTP Error 101 : Cannot open connection
Typically your SMTP server or email program is unable to even start an SMTP session. Possible causes may be : incorrectly spelt SMTP server, invalid IP address, invalid SMTP port or some other process is already using the default SMTP port, port 25.
e.g. «SMTP Error 101, Error opening connection» -or- «SMTP Error 101, cannot open SMTP stream»

SMTP Error 211 : System Status message or System Help Reply
SMTP status 211 prefaces a message about the Mail Server status. You might for example issue a command to the mail server to display a list of commands you can use and the server replies with an SMTP Reply 211 followed by the list you requested.

SMTP Error 214 : Help Reply message
SMTP status 214 is usually in reply to the «HELP» command. It displays information about the server, usually a URL to the FAQ page of the SMTP software running on the server.

SMTP Status 220 : <Server Name> service is running
This is normally the first message you will get back from the server. It means the mail service is running . It will normally contain a welcome message and/or the title of the SMTP software and, sometimes, the version number of the mail server software.

SMTP Error 221 : The domain service is closing the transmission channel

The server is ending the mail session – it is closing the conversation with the ISP as it has no more mail to send in this sending session.
e.g. «221 Closing connection» -or- «221 Goodbye»

SMTP Status 250 : Requested mail action OK completed

The mail server has successfully delivered the message! This is the best SMTP reply to receive — your message has been accepted and transmitted OK !

SMTP Status 251 : User not local will forward to <forward-path>

The email account is not local to the ISP server but the ISP server will accept the email and will forward it.

SMTP Status 252 : Cannot VRFY (verify) the user – the server will accept the message and attempt to deliver it

The user account appears to be valid but could not be verified, however the server will try do deliver the message.

SMTP Error 354 : Start mail input end with <CRLF>.<CRLF>

This is normally in response to the DATA command. The server has received the From and To information and is now asking for the «Message Body», the main part of the message which should be ended by two blank lines separated by a dot (period).

SMTP Error 421 : <Server name> Service not available – the sending email program should try again later

The Mail transfer service is unavailable because of a transient event. It generally indicates that the mail server which returns this status code is currently unavailable but may be available later.

SMTP Error 422 : The recipient’s mailbox is over its storage limit

Either the recipient’s mailbox is over its storage limit or the message delivery directory (folder) on the recipient’s mail server is currently over a size limit imposed by the Network Administrator.

SMTP Error 431 : The recipient’s mail server is experiencing a Disk Full condition

The recipient’s mail server is experiencing a Disk Full error condition, or an Out of Memory error condition.

SMTP Error 432 : The recipient’s Exchange Server incoming mail queue has been stopped

This is an SMTP status response specific to Microsoft Exchange Server. It indicates that the recipient’s mail queue on their Exchange Server has been stopped.

SMTP Error 441 : The recipient’s server is not responding

This is an error emanating from your server indicating that the recipient’s server is not responding. Your server will automatically try again a number of times – how many depends on how your server has been configured.

SMTP Error 442 : The connection was dropped during transmission.

Your server started delivering the message but the connection was broken during transmission. This may be an unusual transient error – however, if it keeps happening you should investigate possible problems which could result in a network connection being broken.

SMTP Error 446 : The maximum hop count was exceeded for the message

The maximum hop count was exceeded for your message. The most likely cause of this error status code is that your message is looping internally on your server, internally between two of your organisation’s servers, or, sometimes, looping between your server and the recipient’s server.

SMTP Error 447 : Your outgoing message timed out.

Your outgoing message timed out because of problems with the receiving server who objected to your message. Typically there is a problem with the message header, such as too many recipients, in most cases, or a protocol timeout between the two servers.

SMTP Error 449 : Routing error

This is a Microsoft Exchange Server specific error code. Possible causes may be : an SMTP connector is configured to use DNS without a smart host and also uses a non-SMTP address space (e.g. X.300), or A message was sent to a recipient who was identified as a member of a routing group that was deleted.

SMTP Error 450 : Requested action not taken – The mailbox was unavailable at the remote end.

In general SMTP Error 450 is a transient error at the remote end, and should induce your mail server to retry after it’s preset retry interval.
e.g. «450 Please try again later» -or- «SMTP Error 450 5.2.3 Msg Size greater than allowed by Remote Host»

SMTP Error 451 : Requested action aborted – Local error in processing.

The action has been aborted by the ISP’s server. «Local» refers to the ISP’s server. This error is usually due to overloading at the ISP from too many messages or transient failures.
e.g. «SMTP error 451 Unable to complete command, DNS not available or timed out» -or- «451 Domain of sender address does not resolve»

SMTP Error 452 : Requested action not taken – Insufficient storage.

The ISP server’s disk system has run out of storage space, so the action had to be cancelled.Sometimes this error may raise if your ISP’s mail server is overloaded from too many messages.
e.g. «452 Out of memory»

SMTP Error 465 : Code Page unavailable on the recipient server

This is an Exchange Server-specific error code. This error is returned by the recipient’s server if the incoming email specifies a Code Page that is not installed on the recipient’s server.

SMTP Error 471 : This is a local error with the sending server and is often followed with «Please try again later»

This is always a local error with your own mail server.It is usually caused by anti-spam or virus scanning software on your server (the sending server) getting into problems through a bug in the software, or because of a bad automatic update from the antivirus/anti-spam manufacturer, because of lack of memory on your server, or because of hard disk problems.

SMTP Error 500 : Syntax error command not recognized.

The last command sent by your server was not recognized as a valid SMTP or ESMTP command, or is not formatted in the way the server expected. This includes situations where the command is too long.

SMTP Error 501 : Syntax error in parameters or arguments (e.g. invalid email address)

The command was correct and recognised, but the parameters (the arguments, e.g. email address) were not valid. For example you try to use invalid email address as sender\@domain.com and as «\» is not allowed in email addresses.

e.g. «Remote host said: 501 Invalid Address»

SMTP Error 502 : Command not implemented.

The command or function issued by your mail server is valid but has not been activated.

SMTP Error 503 : Bad sequence of commands.

In the original standards SMTP Status 503 indicates that the commands have been sent in the wrong order, for example your mail server has sent the «Hello» command before sending the «Mail» command. This can often be caused by a drop in network connection just as your server was sending a command, resulting in the ISP’s server not receiving it and consequently not understanding the command that followed it.

SMTP Error 504 : Command parameter not implemented.

The command and parameter are both valid, but the parameter is not implemented on the ISP server, or an additional parameter or action is missing. For example, an often encountered SMTP Error 504 is : «504 Need to authenticate first».

SMTP Error 510 : Bad Email Address

Bad email address. This status code is generated by the sender’s local mail server.

SMTP Error 511 : Bad Email Address

Bad email address. This error is similar to error 510 and as with error 510, this status code is generated by the sender’s local mail server.

SMTP Error 512 : The host server for the recipient’s domain name cannot be found (DNS error)

This SMTP reply code is received when one of the servers on the way to the destination is unable to resolve the domain name of a recipient email address.

e.g. «SMTP Error 550 5.1.2 Host unknown – host cannot be found»

SMTP Error 513 : Address type is incorrect (most mail servers)

This status code is received if the email addresses are not defined correctly from the sender’s mail server. The may happend due to if a user try to copy and paste the mail addresses from a web page without setting it to correct format. For example the address like receiver(at)domian.com is invalid and should be formated like receiver@domian.com before using.

e.g. «SMTP error 501 5.1.3 Invalid address» -or- «SMTP error 553 5.1.3 User address required !» -or- «SMTP error 501 5.1.3 Bad recipient address syntax»

SMTP Status 523 : The Recipient’s mailbox cannot receive messages this big

This error will be received when the total size of the message you have sent (ie: message + all of its attachments) exceeds the size limits on the Recipient’s server.
e.g. «SMTP Error 450 5.2.3 Message Size greater than allowed by Remote Host» -or- «SMTP Error 552 5.2.3 Data size exceeds maximum permitted» -or- «SMTP Error 552 5.2.3 Message exceeds maximum fixed size»

SMTP Error 550 : Requested actions not taken as the mailbox is unavailable.

SMTP Error 550 will be returned by many servers If the recipient email address simply does not exist on the remote side.

e.g. «550 Invalid recipient» -or- «550 User account is unavailable» -or- «550 No such user here»

SMTP Error 551 : User not local or invalid address – Relay denied.
If neither the sending mail address nor the recipient’s address are locally hosted by the server, then the ISP’s servers may refuse to relay the message on.

SMTP Error 552 : Requested mail actions aborted – Exceeded storage allocation.

The recipient’s mailbox has reached its maximum allowed size.

e.g. «552 sorry, mailbox user@somecompany.com is over quota temporarily (#5.1.1)»

SMTP Error 553 : Requested action not taken – Mailbox name invalid.

There is an invalid email address in the «To», «CC», or «BCC» field of the email message.

SMTP Error 554 : Transaction failed.

There was a permanent error trying to complete the mail transaction which will not be resolved by resending the message in its current form. Some change to the message and/or destination must be made for successful delivery.

Not sure what an SMTP error code means? You’re not alone. It can be shocking and confusing to see SMTP errors sometimes, and we want to eliminate the confusion with a quick-and-easy explanation.

Below, we’ll explain everything you need to know about SMTP error codes, including short explanations of common ones you’ve likely seen before.

What is an SMTP error code?

Within the SMTP process, messages are relayed from one computer to another via SMTP servers. SMTP servers send response codes that indicate what has happened to messages.

While messages are usually sent without issue, different server response codes can indicate various things.

Below are a handful of SMTP server response codes that we’ve compiled that you might see when sending emails.

Common SMTP error codes

• SMTP 250: This SMTP server response simply means everything went well and your message was delivered to the recipient server.
• SMTP 421: Your message was temporarily deferred by the recipient server. This is usually a result of too many connections in a short timeframe or too many messages.
• SMTP 450: Your message was not delivered because the other user mailbox was not available. This can happen if the mailbox is locked or is not routable.
• SMTP 451: This response is sent when the message simply failed. Often times this is not caused by you, but rather because of a far-end server problem.
• SMTP 452: This kind of response is sent back when there isn’t enough system storage to send the message. Your message is deferred until storage opens up and it can then be delivered.
• SMTP550: The message has failed because the other user’s mailbox is unavailable or because the recipient server rejected your message.
• SMTP 551: The mailbox your message was intended for does not exist on the recipient server.
• SMTP 552: The mailbox your message was sent to does not have enough storage to accept your message.
• SMTP 553: Your message was not delivered because the name of the mailbox you sent it to does not exist.
• SMTP 554: This is a very vague message failure response that can refer to any number of problems either on your end or with the recipient server.

There are a variety of issues that can trigger these SMTP server responses, and you’re not expected to know how to handle all of them. SendGrid’s amazing support staff is here to help you figure out what went wrong and what you can do to correct it.

Start sending with Twilio SendGrid

To learn more about these and other SMTP server responses, read our Knowledge Base article. The article provides examples of all these responses as well as offers suggestions for correcting any problems.

Sending email involves multiple computers communicating with each other through a process call Simple Message Transfer Protocol (SMTP). SendGrid functions as an SMTP relay service to send billions of marketing and transactional emails every month.

Sign up for a free account (no credit card required) to start sending!