Understand wrong email messages (user unknown, host not found, undeliverable...) (2023)

The error messages you sometimes get after sending aEmailThey are often in English and unintelligible even to those fluent in Shakespeare's language. I'll try to put things simply for you. Experts will assign abbreviations used for educational purposes.

To draw a parallel with the post office, we can imagine thathostlike oneEmail Sorting Center. Each city has one or more mail sorting centers, and each location has a sorting center forE-Mailsin which he officiates what we"electronic factor».

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Remember that nowadays the character case (lowercase and uppercase letters) no longer plays a role in one directionEmail.

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Here are some error messages that you may encounter along with their meaning:

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English standard error messagetranslationMeaning
  • courier delivery system.
  • email distribution system.
The “electronic factor” in a way.
  1. Undeliverable correspondence returned to sender.
  2. delivery errorÖDelivery failedÖtransmission error.
  1. Return to sender.
  2. distribution error.
There was an error processing your message. The "electronic postman" who noticed this error will send you a message informing you about the error found, mostly in English.
  • The original message continues.
  • Here is his original post.
The message you originally sent is retrieved for your information (in its original form).
  • message truncated.
  • message truncated.
If the error message is similar to the original message, the end of the message may have been truncated to prevent the error message from becoming too large.
  • Delivery report.dat
  • A detailed delivery report can be found in the attached file named "Delivery Report.dat".
Attached file with detailed report of found errors. You can open this file, for example, with the Windows software "Notepad" or your usual word processing program. Be careful as some fake error messages contain a "Delivery Report.dat" file..vbs(or other derived names) infected with a virus.Messages related to SMTP error code 550 5.1.1
  1. Unknown User.
  2. There is no such user here.
  3. This user does not have a yahoo.fr account.
  4. Message rejected (no valid recipients).
  5. Invalid container.
  6. User not found.
  7. Unfortunately, there is no mailbox with this name here.
  8. ...is not a valid mailbox.
  9. Requested action not taken: Mailbox unavailable.
  10. Recipient address rejected: Unknown user in the local recipient table.
  11. The email account you tried to access does not exist.
  1. Unknown User.
  2. This user does not exist.
  3. This user does not have a yahoo.fr email account.
  4. Rejected message (no user matches).
  5. Wrong recipient.
  6. User not found.
  7. Unfortunately, there are no mailboxes with this name here.
  8. ...is not a valid mailbox.
  9. Request not executed: Mailbox not available.
  10. Recipient address denied: Unknown user in the local recipient list.
  11. The examEmailthe one you tried to access does not exist.
Either you made a mistake in your correspondent's address in the "Username" section, or your correspondent's email inbox was deleted.
Check your spelling and try again if it's wrong. You can see if you didn't miss a point somewhere, or if you confused the line from 6 with the line from 8...
  1. I am sorry to report that the reply message below could not be delivered to one or more recipients.
  2. A message you sent could not be delivered to one or more recipients. This is a permanent error. The following addresses failed.
  3. The message could not be delivered to the following addresses.
  4. Delivery to the following recipients permanently failed.
  1. I am sorry to inform you that your message copied below could not be delivered to one or more recipients.
  2. A message you sent could not be delivered to one or more recipients. It's a permanent bug. The following addresses are problematic.
  3. Delivery to the following recipients failed.
  4. The delivery to the following recipients definitely failed.

One or more recipients of your message did not receive your message. This error message is usually followed by another message of the type described below, containing the email addresses that caused the error.

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Messages related to SMTP error code 550 5.2.1
  • Mailbox disabled, not accepting messages.
  • Mailbox deactivated, no longer accepting messages.
Your interlocutor's e-mail inbox has been deactivated, probably because he has not been able to access it for a long time. You just have to try to reach him in other ways. You can wake up your box simply by connecting to it.Messages related to SMTP error code 544 5.4.4
  1. Host not found.
  2. Unknown host.
  3. Recipient address rejected: Domain not found.
  1. Host not found.
  2. Unknown host.
  3. Recipient address rejected: Domain (or host) not found.
Either you made a spelling mistake at your correspondent's host level, or your correspondent's "electronic factor" is defective. Check the host's spelling and try again.
It is also possible that your correspondent's host no longer exists. Check if the relevant website is still online.Messages related to SMTP error code 552 5.3.4
  • The message size exceeds the specified maximum message size.
  • The message size exceeds the maximum allowed size.
You are attempting to send a message that is too large (due to attachments) to exceed the limits set by your or the recipient's email system. If possible, send your attachments in installments or use a service likedl.free.fr.Messages related to SMTP error code 452 4.2.2 or 552 4.2.2
  1. You have exceeded the disk quota.
  2. about the fee.
  3. mailbox full.
  1. The disk space quota has been exceeded.
  2. Quota exceeded.
  3. mailbox full.
The e-mail inbox of the person you are talking to is full. All that remains is to send him a clearer message (e.g. without a photo) or call him and ask him to delete the messages from his inbox to free up space and be able to receive messages again...
You can receive this message without writing to anyone. It is then your own email account that is saturated. Go to you quicklyEmailto free up space by deleting messages. So if you use an email software (e.g. Outlook, Thunderbird...), you can optionally adjust the settings "Keep messages on the server" and "Delete messages from the server after XX days".Messages related to SMTP error code 451 4.4.1 or 451 4.4.2
  1. This is just a warning message. You don't have to forward your message.
  2. Warning: The message could not be sent in the last 4 hours.
    Warning: The message could not be sent in the last 4 hours.
  1. This is just a warning message. You don't have to forward your message.
  2. Warning: This message could not be sent in the last 4 hours.
The "electronic postman" of your interlocutor does not answer. So your message has been pending for 4 hours. Reps run automatically and regularly for a total of 5 days (leave and wait). After this period, your message will be destroyed. You will get a new error message. You can then try sending a message again, hoping that your correspondent's "postman" will be up and running again.Messages related to SMTP error code 450 4.1.8
  • Sender address rejected: Domain not found.
  • Sender address denied: Domain (or host) not found.
Your email software is probably misconfigured (your sender address was entered incorrectly on the host). Please check, correct and try again.Messages related to SMTP error code 550 or 554
  1. Access denied.
  2. Connection refused.
  3. Email rejected by Windows Live Hotmail for policy reasons. The email server IP associated with Windows Live Hotmail showed namespace mining behavior.
  4. Delivery temporarily suspended.
  5. Messages from xxxxx temporarily postponed due to user complaints.
  1. Offer rejected.
  2. Connection refused.
  3. Message rejected byWindows Live Hotmail. The IP address of the connected email serverWindows Live HotmailBulk Spam Attempt.
  4. Sales temporarily suspended.
  5. Messages sent by xxxxx are temporarily denied due to user complaints.

Your host has probably been banned (possibly temporarily) by the recipient's host for being too lax about spammers. The easiest way is to write to your correspondent from a different address (with a different host). You can also wait 4 hours (temporary ban, seeyahoo!) and try sending the message again using your original address.

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  • Email rejected by Windows Live Hotmail for policy reasons. Rejection reasons can be related to spam content or IP/domain reputation issues.
  • Unfortunately, messages from [xxx.xxx.xxx.xxx] were not sent. Please contact your ISP as part of their network is on our block list (S3140).
  • Client host rejected: Abuse detected GU_EIB_04
  • Spam detected
  • Mail rejected byWindows Live Hotmailin accordance with its anti-spam policy. The reasons for this rejection may be related to the message looking like aSpam, or that the IP address or the sending domain is considered the senderSpam.
  • Unfortunately, messages from [xxx.xxx.xxx.xxx] were not delivered. Please contact your ISP as part of their network is on our block list (S3140).
  • Sender Rejected: Abuse Detected (GU_EIB_04) (message noted when writing to an address SFR, Cegetel etc.).
  • Spam detected
Your message was blocked and rejected because it either looked like aSpam, or because your host is known to broadcastSpam. Try changing the content of your message (simplify, remove unnecessary links...), or send it from an address with a different host.Messages related to SMTP error code 451, 550, or 554
  • Too many errors from your IP.
  • Start errors from your IP address.
You probably sent the same message to many recipients (From you) and unfortunately many addresses are wrong. This is a situation spammers often face who don't keep their lists up to date. Hence, it is suspected as spam and delayed by the electronic factor.
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Why is my email address saying undeliverable? ›

Undeliverable. If you receive an error that a message is undeliverable, this could be due to the sending server trying to deliver the message, but the action didn't complete before the message expired. This error typically indicates a problem on the receiving server.

How do I fix undeliverable email? ›

Troubleshooting Undelivered Emails
  1. Double-check the email address. ...
  2. Check the status of the email in the Events tab. ...
  3. Ask client to check their spam folder. ...
  4. Ask client to perform a search. ...
  5. Ask client to add your email address to their contact list. ...
  6. Ask client to contact their ISP. ...
  7. Optimize your emails for deliverability.
Sep 27, 2019

Why am I getting undeliverable email about emails I didn t send? ›

Spammers sometimes impersonate another user in the From address when they send out mail. They may send unwanted email to millions of addresses, and any bounced messages then get sent to you (these bounced emails you get are called backscatter).

What can be the reason if you receive a user unknown reply to an e mail you sent? ›

It is an error code that usually stands for some issue with the recipient server. The most frequent error message is “ User unknown ”. In most cases, this is because the recipient address does not exist.

Why is my email address rejecting emails? ›

When you send an email and get an “address rejected” error message, it means the email server can't verify your email address because the SMTP server authentication feature is disabled in your email client.

Does undeliverable mean blocked? ›

If the email is bounced back to you as “undeliverable” it could mean that the receiving email server is temporarily unavailable, overloaded or simply couldn't be found. If the server has crashed or is under maintenance (in other words, temporarily unavailable), you will need to wait to send the email again.

How do I resend undeliverable messages? ›

Double-click the message that you want to resend. On the Message tab, in the Move group, click Actions, and then click Resend This Message. Tips: When the new message displays, you can: Remove recipients who don't need to receive the message again.

What does an undeliverable email look like? ›

Listing of the Most Common Error Undeliverable Email Codes:

251 User not local: will forward to 421 Service not available, closing transmission channel. 450 Requested mail action not taken: mailbox unavailable (E.g., mailbox busy) 451 Requested action aborted: local error in processing.

What malware sends out emails? ›

Macro virus.

It is transmitted through a phishing email message containing a malicious attachment. As users share the infected documents with others, often by forwarding the email, the virus spreads and infects additional devices.

Is my email being spoofed? ›

Email spoofing is when the sender of the email forges (spoofs) the email header's from address, so the sent message appears to have been sent from a legitimate email address. If you have received a high volume of undeliverable notices in your inbox, there is a strong chance your email address is being spoofed.

What is the best thing to do when you received an unsolicited email from an unknown sender? ›

The basic rule of thumb is Ignore, Delete and Forget such email. There are no simple ways of stopping such emails.

What message does a blocked email address get? ›

When you block emails, you are creating a filter in the email app that sends all messages from that email address to a spam or junk folder. You'll still receive messages from blocked senders in your mailbox. However, the message sender is never notified that they've been blocked and that you don't read their email.

What are the three common reasons why a message may be rejected? ›

The recipient email address doesn't exist, or is incorrect, so we cannot deliver the message. The sender must resend the message to a valid email address. An anti-virus signature has been triggered, and the message is categorized as malware.

How do I stop emails from being blocked? ›

Here are 15 do's and don'ts to avoid having your email blocked or blocklisted:
  1. Don't buy email lists. ...
  2. Do use double opt-in to confirm email list subscribers. ...
  3. Don't repeatedly send the same or similar content. ...
  4. Don't string readers along with vague content. ...
  5. Don't send attachments, it's a sure way to get blocked.
Jan 18, 2016

Can you tell if someone blocked your email? ›

Blocked emails automatically go to the spam folder of your Gmail. So, you don't have a bother in your inbox. Furthermore, if an email is blocked by numerous users worldwide or their sending limit is often exceeded, Google will automatically put such emails in your spam folders.

Why would something be undeliverable? ›

A package might be returned as undeliverable for several reasons: The address is incorrect or outdated. Usually, the package is stored for a period that can vary depending on the courier who holds it and then returns it to us. Double-check the address carefully when placing your order.

Does the sender know if an email is blocked? ›

If you've added an email address to your Blocked senders list, they will not get any notification that will inform them they have been blocked. You will simply not receive any of their messages.

What is the best way to resend an email? ›

Using Reply
  1. Head over to your “Sent” folder and find the email you want to resend.
  2. Click “Reply.”
  3. Edit the body of the email to remove any content that's no longer relevant (or to add in anything new that is).
  4. Remove the subject line, then add the recipient.
  5. Click “Send.”
Feb 3, 2022

Does undeliverable mail get returned? ›

Mail doesn't get delivered for lots of reasons: the address is illegible, the sender hasn't put on enough postage, or the person doesn't live at the address any longer, among other reasons. If there's a return address, the U.S. Postal Service will return it to the sender.

How do you resend an email that was not answered? ›

How to Write a Follow-Up Email After No Response
  1. Ask yourself if you included a close in your first attempt.
  2. Resist the urge to re-send your first email.
  3. Don't follow up too quickly.
  4. Write a truthful subject line.
  5. Start the message with a reminder of your last touchpoint.
Mar 14, 2022

Can a hacker access your emails with your email? ›

One of the major risks of scammers having your email address is that they'll use it to hack into your other online accounts. With your email address, they can request password resets, try entering your other passwords that have been leaked online, and even break into your email account.

What are three signs of malware? ›

Here are a few telltale signs that you have malware on your system:
  • Your computer slows down. ...
  • Your screen is inundated with annoying ads. ...
  • Your system crashes. ...
  • You notice a mysterious loss of disk space. ...
  • There's a weird increase in your system's Internet activity. ...
  • Your browser settings change.

What happens if you open a malware email? ›

Clicking on a phishing link or opening an attachment in one of these messages may install malware, like viruses, spyware or ransomware, on your device. This is all done behind the scenes, so it is undetectable to the average user.

Can you get hacked by opening an email on your phone? ›

Through a suspicious email, the hacker can put malware on your computer or mobile device. This malware can track you and gain access to even more of your personal information.

How do hackers send email from my email address? ›

How Spammers Spoof Your Email Address. Spoofing is the act of forging an email address, so it appears to be from someone other than the person who sent it. Often, spoofing is used to trick you into thinking an email came from someone you know, or a business you work with, like a bank or other financial service.

What does a malicious email look like? ›

Most malware emails appear to be package delivery notices, invoices, fax/scans, or court notices. These emails rarely appear to come from an appropriate address, for example emails claiming to be from Fedex or UPS are likely to be malware if their From address does not match fedex.com or ups.com.

Should you respond to unknown emails? ›

Do not reply to any mysterious email with an unknown subject and sender. This simply confirms to the sender that somebody is reading the mail. Similarly, do not click any links embedded in the message. Once you perform the email confirmation, there is no way to reverse the confirmation process.

How do scammer get your email address? ›

There are several common ways that spammers can get your email address:
  • Crawling the web for the @ sign. Spammers and cybercriminals use sophisticated tools to scan the web and harvest email addresses. ...
  • Making good guesses… and lots of them. ...
  • Tricking your friends. ...
  • Buying lists.
Aug 6, 2010

Should I unsubscribe from spam emails? ›

Don't ever click the “unsubscribe” option in spam

That link could connect you to a fake site attempting to steal your account details or to stealth malware, such as a virus or trojan program, that will install itself your device without your knowledge.

What does a sender see when blocked? ›

When you block a contact over Android or iPhone, they will still be able to send you text messages. These messages will not show up on your phone but the sender will see the messages as sent. They won't know that they've been blocked.

What happens when a blocked person sends an email? ›

The blocked person can still send you mail, but if anything from his or her email address makes it to your email account, it's immediately moved to the Junk Email folder. Future messages from this sender will go to your Junk Email folder or End-User Quarantineif enabled by your administrator.

What does message from unknown sender mean? ›

UNKNOWN SENDER means, the person who sent you message is not in your contact list.

What does unknown user mean? ›

Unknown users are invalid or unrecognized email addresses in a sender's database. When you deploy an email to an email address that does not exist, a 5xx 5. x.x error message will appear in your Simple Mail Transfer Protocol (SMTP) bounce logs with a description such as: Unknown user. No such user.

What does unknown in email means? ›

“Unknown” is the result code that is used for anything but a conclusive result (i.e. anything other than “verified”, “undeliverable”, “unreachable”, “illegitimate” or “disposable”).

What should you do when you receive an email from a unknown contact with an attachment )? ›

If you receive a phishing email
  1. Never click any links or attachments in suspicious emails. ...
  2. If the suspicious message appears to come from a person you know, contact that person via some other means such as text message or phone call to confirm it.
  3. Report the message (see below).
  4. Delete it.

Should I open an email from an unknown sender? ›

Here are some important things to know about email attachments before opening them. Attachments from Unknown Senders – Never open an attachment from an unknown or sender to avoid exposing your computer to viruses, worms, and Trojans.

Should I open a message from an unknown number? ›

BBB said these scammers potentially have technology to steal your phone contacts and continue to scam your friends too, so avoid even opening up the unknown text.

What do you do when it says user not found? ›

This might also cause you to get the “user not found” message when trying to access the profile because you've missed a letter or character in their username. You can fix this by asking the user to type and send their username or profile link to you.

How do you remove unknown users? ›

Step 3. Remove the Unknown Account from your PC.
  1. Login on your PC using an account with Admin privileges.
  2. Simultaneously press the Win + R keys to open the run command box and type. control userpasswords2.
  3. Select the Unknown account in the list and click remove.

What happens when it says user not found? ›

If a person has temporarily disabled their account and you're trying to look them up, you'll see the “User not found” message. You can confirm whether this is the reason you're seeing this message by asking one of your mutual followers to look up the profile you're trying to access.

What happens if you open an unknown email? ›

The good news is that opening a suspicious email, while not ideal, is relatively harmless. Spam emails only become a serious cyber threat if you've committed any of the following actions: Downloaded any malicious files or email attachments.

How do I check my phone for malware? ›

How to check for malware on Android
  1. Go to the Google Play Store app.
  2. Open the menu button. You can do this by tapping on the three-line icon found in the top-left corner of your screen.
  3. Select Play Protect.
  4. Tap Scan. ...
  5. If your device uncovers harmful apps, it will provide an option for removal.

How do I check my iPhone for malware? ›

How to check your iPhone for malware
  1. Look for unfamiliar apps. If you're anything like the average smartphone user, you've probably downloaded dozens (if not hundreds) of apps. ...
  2. Check your data usage. ...
  3. Check power consumption. ...
  4. Keep an eye on pop-up ads. ...
  5. Scan your phone using antivirus software.
Nov 6, 2022

How do you check if an email is legit? ›

5 ways to detect a phishing email – with examples
  1. The message is sent from a public email domain. No legitimate organisation will send emails from an address that ends '@gmail.com'. ...
  2. The domain name is misspelt. ...
  3. The email is poorly written. ...
  4. It includes suspicious attachments or links. ...
  5. The message creates a sense of urgency.
Mar 22, 2022


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