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

FAQs

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

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.

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.

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

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.

“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”).

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.

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.

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.

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.