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Avoid clicking links in emails like Undelivered Mails email scam

Also Known As: Undelivered Mails spam
Damage level: Medium

What is Undelivered Mails scam?

Scammers use email as a tool for various purposes. One of them is to trick recipients into providing personal information. Emails of this type are called phishing emails.

Typically, scammers behind emails of this type pretend to be legitimate companies and try to trick recipients into providing login credentials (for example, usernames, passwords), credit card details (for example, cardholder name, CVV code, expiry date), social security numbers or other sensitive details.

It is common that scammers use deceptive websites to trick users into providing information. For example, they disguise fake login pages as legitimate, official sites. In one way or another, emails (and links in them) of this type should be ignored.

Undelivered Mails Scam email spam campaign

More about the Undelivered Mails scam

This email is disguised as a letter from email service provider (Webmail). Scammers behind it attempt to trick recipients into believing that twelve emails were not delivered due to a system delay and clicking the "Click Here To Release Pending Messages Inbox" hyperlink.

The provided link opens a deceptive website asking to enter login credentials (email address and password). There are many examples of similar phishing emails that scammers use with the purpose to steal email accounts.

It is common that scammers check accessed accounts for important emails containing sensitive information, use them to trick other people into making money transactions, providing personal information, and for other malicious purposes (e.g., to send spam, malspam). Another problem with having an email (or other) account stolen is that its login credentials could be used to access other accounts (e.g., social media, gaming accounts).

Although, it is a problem only when users use the same login credentials for multiple accounts (for this reason, it is recommended to use different passwords for different accounts).

Threat Summary:
Name Undelivered Mails Scam
Threat Type Phishing, Scam, Social Engineering, Fraud
Fake Claim Twelve emails were not delivered due to a system delay
Disguise Letter from email service provider
Symptoms Unauthorized online purchases, changed online account passwords, identity theft, illegal access of the computer.
Distribution methods Deceptive emails, rogue online pop-up ads, search engine poisoning techniques, misspelled domains.
Damage Loss of sensitive private information, monetary loss, identity theft.
Malware Removal (Windows)

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Examples of similar scams

More examples of phishing emails are "BANCO BPM Email Scam", "Emails Rejected On Admin Server Scam", and "New App(s) Have Access To Your Microsoft Account Email Scam". What most of them have in common is that they are designed to look like letters from legitimate entities and include suspicious attachments or links.

As mentioned in the first paragraph, scammers use phishing emails to extract login credentials, credit card details, and other sensitive information that could be used to steal identities, make unauthorized purchases, transactions, and for other malicious purposes. It is important to mention that email can be used as a tool to distribute malware.

Emails used to deliver malware are quite similar to emails used to extract sensitive information. A couple of examples of emails that cybercriminals use to trick recipients into installing malware on their computers are "Santander Email Virus", "Contech Email Virus", and "Air Sea Land Email Virus".

How do spam campaigns infect computers?

As a rule, emails used to deliver malware contain a malicious attachment or link. In both cases, the main purpose of these emails is to trick recipients into downloading and opening a malicious file.

Typically, cybercriminals behind emails of this type attempt to trick recipients into opening/executing a malicious file extracted from ZIP, RAR or another file, Microsoft Office document, PDF document, executable file (like EXE), or JavaScript file. It is important to mention that cybercriminals try to trick recipients into believing that the received file is some important document (e.g., a purchase order, invoice).

In one way or another, it is strongly recommended not to open files or click links in emails of this kind. It is worthwhile to mention that not all malicious documents infect computers automatically.

If opened with MS Office 2010 or later, those documents need to get permission to enable macros commands (editing or content). Although, older MS Office versions do not have the "Protected View" mode that prevents opened malicious documents from installing malware without needing any user's interference.

How to avoid installation of malware?

Emails including links or attachments should be thoroughly analyzed, especially if they are received from an unknown sender and are not relevant. It is common that emails of this type are used to deliver malware - cybercriminals behind them seek to trick recipients into opening malicious files.

Files and programs should be downloaded only from official pages and via direct links. Other sources can be used to distribute malicious files/programs. Examples of questionable sources are Peer-to-Peer networks (like torrent clients, eMule), unofficial websites, third-party downloaders, free file hosting sites.

It is worth mentioning that third-party, fake installers can be used to distribute malware too. One more important thing is not to use third-party, unofficial tools to activate or update software.

Quite often, those tools are bundled with malware (used to distribute malicious software). Another problem is that it is illegal to activate legitimate software with 'cracking' tools.

Installed programs have to be activated, updated with tools or functions that their official developers provide. Additionally, it is recommended to scan the operating system threats regularly and do it using a reputable antivirus or anti-spyware software.

If you've already opened malicious attachments, we recommend running a scan with Combo Cleaner Antivirus for Windows to automatically eliminate infiltrated malware.

Text presented in the Undelivered Mails Scam email letter:

Subject: ACCOUNT WARNING: Undelivered mails ******** Kindly rectify

Dear ********
You have [12] undelivered mails on 6/6/2021 7:19:35 a.m. This was caused due to a system delay, Rectify Below:

Click Here To Release Pending Messages Inbox

Product: ********  WebMail

Yet another example of undelivered mail-themed spam promoting a phishing site:

Undelivered mail-themed spam (2021-08-13)

Text presented within:

Subject: You have 4 non delivered e-mails

 

Attention ********,

You have {4} undelivered mails as at ********

This is due to some technical system error from Mail Server.

Please update/confirm e-mail ******** below to enable it receive your pending mails into your mailbox within 48hrs

Confirm Now

Sincerely
Mail support team.

Yet another example of undelivered mails-themed scam promoting a phishing website:

Undelivered mails-themed spam

Text presented within:

Subject: Resolve.ID #16,301134zi50


MAIL SUPPORT

Hi -,

You have (9) undelivered messages that failed to deliver to your inbox as of 9/28/2021 7:59 PM.

Follow the link below to release messages to inbox.

Release Messages

The link above will expire in 24 hours

Have a great day!

Another example of mail delivery-themed scam:

Mail delivery failure-themed spam (2021-11-12)

Text presented within:

Subject: 3rd Notice : 12 incoming mails could not be delivered : please review!!!

Dear - ,

You have reached your E-Mail storage bandwidth limit for account -.   Most of your incoming mails will now be placed on hold.
 
CLICK TO RE-VALIDATE YOUR EMAIL

After re-validating your email account all your incoming emails on hold will be delivered to your mailbox.

Regards.
Email Account Server {C} 2021

-

This message is auto-generated from E-mail - security server, and replies sent to this email can not be delivered.

Screenshot of the promoted phishing site:

Phishing site promoted via mail delivery failure-themed spam (2021-11-12)

Another example of undelivered mail-themed spam promoting a phishing site:

Undelivered mail-themed spam promoting a phishing website (2021-11-19)

Text presented within:

Subject: Release Undelivered Mail

Email Delivery Notice
 
User:  -

You have 7 undelivered mail
Time : 11/18/2021 5:12:40 p.m.
This is due to a system error
 
Release All Undelivered Mail
 
However, if you do not release all undelivered mail, it will be completely wiped from - data base.

- Support Team
 

This message is auto-generated from E-mail security server, and replies sent to this email can not be delivered.This email is meant for: -

Copyright © 2021 - • Web Admin •

Screenshot of the promoted phishing site:

Phishing site promoted via Undelivered mail-themed spam (2021-11-19)

Yet another example of undelivered mail-themed spam spreading an HTML file used for phishing purposes:

Undelivered mail-themed spam (2021-12-07)

Text presented within:

Subject: You have (4) pending messages

 

New notification for "-".

    
You have (4) new pending messages from your inbox because this version will soon expire, Please download attachment for the new version for free as soon as possible in order to prevent the loss of  any future emails.

The system generated this notice on 2021/06/12

Do not reply to this automated message.

Screenshot of the attached HTML file ("New_Version.html"):

HTML file distributed using undelivered mail-themed spam (2021-12-07)

Another example of unsuccessful mail delivery-themed spam email used to promote a phishing site:

Your sent message was not delivered to recipient's inbox spam

Text presented withing:

Subject: Message Delivery Report (Wednesday, 09 March, 2022)

Your sent message was not delivered to recipient's inbox.
DELIVER MESSAGE INBOX NOW

Microsoft ®

© 2022
Unsubscribe

Screenshot of the promoted phishing site (fake Microsoft website):

Phishing site promoted via Your sent message was not delivered to recipient's inbox spam

Another example of undelivered pending mail-themed spam used to promote a phishing site:

Pending email-themed spam

Text presented within:

Subject: Mail System Error - Returned Mail - ********


Dear: ********

1 pending sent messages couldn't be delivered

* Action Required.    
* How to Fix It.

Click here to view undelivered sent messages.

Created Date: 4/6/2022 1:00:00 p.m.
********  Your best Mail Service.

Screenshot of the promoted phishing site:

Phishing site promoted via pending email-themed spam

Another example of undelivered mail-themed spam used to promote a phishing site:

Undelivered mail-themed spam (2022-04-26)

Text presented within:

Subject: Undelivered Mail Returned to Sender


This is the mail system at host ********.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. Details.

You can find the the possible reasons of the undelivered message letter here:
View Emails

Please, do not reply to this message.

Host or domain name not found.
Name service error for name=xn--baslangc-zkb.com.tr type=AAAA: Host not found

Reporting-MTA: dns; forward103p. ********.
X-Yandex-Queue-ID: 1BA7718C0BB8
X-Yandex-Sender: rfc822; ********
Arrival-Date: Wed, 26 APR 2022 14:12:19 +030

Screenshot of the promoted phishing site:

Phishing site promoted via undelivered mail-themed spam (2022-04-26)

Another example of undelivered mail-themed spam promoting a phishing site:

Undelivered mail-themed spam (2022-05-14)

Text presented within:

Subject: Notification - Incoming Error


Incoming Server Error

-

The mail server encountered an error and failed to deliver your incoming important (12) emails. Some incoming messages (12) are stuck on the server.


Kindly use the button below to fix the error.

Retrieve (12) Emails to Inbox

Email is strictly for the attention of -
Copyright© 2022 -

Yet another example of undelivered mail-themed spam promoting a phishing site:

Undelivered mail-themed spam (2022-06-21)

Text presented within:

Subject: You Have (7) New Undelivered Messages


Dear ********,

You have (7) new undelivered mail due to some error in ********  IMAP/POP3 mail server. We recommend you move messages to inbox and fix errors immediately to avoid more blockage.
 
Move message to inbox


All messages will deleted automatically without no response pending additional verification to free up your storage capacity and release all your pending messages.
******** web service.

Yet another example of undelivered mail-themed spam promoting a phishing site:

Undelivered mail-themed spam used to promote a phishing site (2022-09-08)

Text presented within:

Subject: Message Server Failure!
 
You have undelivered messages.     

You have 15 emails not delivered to your inbox on 06/09/2022
This is because your  - account has exceeded the
disk space limit. To avoid disruptions of your Email Services, add disk space to release undelivered Email messages to your inbox.


RELEASE MESSAGES  
ADD DISK SPACE HERE

-  server

Screenshot of the promoted phishing site:

Phishing site promoted via Undelivered mail-themed spam (2022-09-08)

Yet another example of an email from "Undelivered Mails" spam campaign:

Undelivered Mails-themed spam (2023-02-22)

Text presented within:

Subject: Action required ********

 

******** Notification.

You have (25) incoming messages that could not be delivered to ********

Kindly resolve these email issues to avoid missing important mails.

********     ********     25 messages
Action Required Pending
    
High Priority.

Proceed To Resolve

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Quick menu:

Types of malicious emails:

Phishing email icon Phishing Emails

Most commonly, cybercriminals use deceptive emails to trick Internet users into giving away their sensitive private information, for example, login information for various online services, email accounts, or online banking information.

Such attacks are called phishing. In a phishing attack, cybercriminals usually send an email message with some popular service logo (for example, Microsoft, DHL, Amazon, Netflix), create urgency (wrong shipping address, expired password, etc.), and place a link which they hope their potential victims will click on.

After clicking the link presented in such email message, victims are redirected to a fake website that looks identical or extremely similar to the original one. Victims are then asked to enter their password, credit card details, or some other information that gets stolen by cybercriminals.

Email-virus icon Emails with Malicious Attachments

Another popular attack vector is email spam with malicious attachments that infect users' computers with malware. Malicious attachments usually carry trojans that are capable of stealing passwords, banking information, and other sensitive information.

In such attacks, cybercriminals' main goal is to trick their potential victims into opening an infected email attachment. To achieve this goal, email messages usually talk about recently received invoices, faxes, or voice messages.

If a potential victim falls for the lure and opens the attachment, their computers get infected, and cybercriminals can collect a lot of sensitive information.

While it's a more complicated method to steal personal information (spam filters and antivirus programs usually detect such attempts), if successful, cybercriminals can get a much wider array of data and can collect information for a long period of time.

Sextortion email icon Sextortion Emails

This is a type of phishing. In this case, users receive an email claiming that a cybercriminal could access the webcam of the potential victim and has a video recording of one's masturbation.

To get rid of the video, victims are asked to pay a ransom (usually using Bitcoin or another cryptocurrency). Nevertheless, all of these claims are false - users who receive such emails should ignore and delete them.

How to spot a malicious email?

While cyber criminals try to make their lure emails look trustworthy, here are some things that you should look for when trying to spot a phishing email:

  • Check the sender's ("from") email address: Hover your mouse over the "from" address and check if it's legitimate. For example, if you received an email from Microsoft, be sure to check if the email address is @microsoft.com and not something suspicious like @m1crosoft.com, @microsfot.com, @account-security-noreply.com, etc.
  • Check for generic greetings: If the greeting in the email is "Dear user", "Dear @youremail.com", "Dear valued customer", this should raise suspiciousness. Most commonly, companies call you by your name. Lack of this information could signal a phishing attempt.
  • Check the links in the email: Hover your mouse over the link presented in the email, if the link that appears seems suspicious, don't click it. For example, if you received an email from Microsoft and the link in the email shows that it will go to firebasestorage.googleapis.com/v0... you shouldn't trust it. It's best not to click any links in the emails but to visit the company website that sent you the email in the first place.
  • Don't blindly trust email attachments: Most commonly, legitimate companies will ask you to log in to their website and to view any documents there; if you received an email with an attachment, it's a good idea to scan it with an antivirus application. Infected email attachments are a common attack vector used by cybercriminals.

To minimise the risk of opening phishing and malicious emails we recommend using Combo Cleaner Antivirus for Windows

Example of a spam email:

Example of an email spam

What to do if you fell for an email scam?

  • If you clicked on a link in a phishing email and entered your password - be sure to change your password as soon as possible. Usually, cybercriminals collect stolen credentials and then sell them to other groups that use them for malicious purposes. If you change your password in a timely manner, there's a chance that criminals won't have enough time to do any damage.
  • If you entered your credit card information - contact your bank as soon as possible and explain the situation. There's a good chance that you will need to cancel your compromised credit card and get a new one.
  • If you see any signs of identity theft - you should immediately contact the Federal Trade Commission. This institution will collect information about your situation and create a personal recovery plan.
  • If you opened a malicious attachment - your computer is probably infected, you should scan it with a reputable antivirus application. For this purpose, we recommend using Combo Cleaner Antivirus for Windows.
  • Help other Internet users - report phishing emails to Anti-Phishing Working Group, FBI’s Internet Crime Complaint Center, National Fraud Information Center and U.S. Department of Justice.

Frequently Asked Questions (FAQ)

Why did I receive this email?

Cybercriminals may have acquired your email address through a data breach. Phishing emails are not personal. Usually, they are sent randomly to a large number of email addresses.

I have provided my personal information when tricked by this email, what should I do?

If you have provided your username and password to scammers, change your passwords as soon as possible. Also, contact the service provider for the affected account and inform them of the situation.

I have downloaded and opened a malicious file attached to an email, is my computer infected?

If the file was executable, then the likelihood of infection is high. However, if it was a document in formats such as .pdf or .doc, you may have avoided infection since merely opening the document does not always lead to malware infiltrating the system.

I have read the email but didn't open the attachment, is my computer infected?

Merely opening an email is entirely safe. However, clicking on links within the email or opening attachments can result in system infections.

Will Combo Cleaner remove malware infections that were present in email attachment?

Combo Cleaner has the ability to detect and remove nearly all known malware infections. Sophisticated malware typically conceals itself deeply within the system. Thus, it is imperative to perform a complete system scan to ensure proper detection and removal.

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About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

PCrisk security portal is brought by a company RCS LT. Joined forces of security researchers help educate computer users about the latest online security threats. More information about the company RCS LT.

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Malware activity

Global malware activity level today:

Medium threat activity

Increased attack rate of infections detected within the last 24 hours.

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