How to spot scams like "Security Check - Mail Delivery Failure Notice"

What is "Security Check - Mail Delivery Failure Notice"?

We have inspected the email and concluded that it is designed to appear as a "delivery failure notice" from the email service provider. It includes a link to a fake login website designed to steal personal information. Victims of this scam may lose access to email accounts and encounter further issues.

More about the "Security Check - Mail Delivery Failure Notice" scam email

The scam email claims that the recipient's outgoing messages are being rejected and that some emails sent from the account are not reaching recipients. It states this is caused by authentication problems or a temporary block.

It claims the affected account recently experienced a failed delivery due to "DMARC or SPF misalignment". The message urges the recipient to verify account settings through the provided button (labeled "Verify Account & Resume Delivery") to restore normal email delivery. Clicking this button/link opens a fake website.

That page is designed to look like an email account login website and steal email addresses and passwords. This information can be used to hijack email accounts and use them to steal information, send deceptive emails, distribute malicious software, or for other malicious purposes.

Also, scammers may attempt to hijack other accounts, including social media, banking, or gaming. This could lead to other issues, such as identity theft or financial loss. Thus, suspicious emails should be examined before disclosing personal information.

Similar scam emails in general

Scams like this are often disguised as important emails from legitimate services or other entities. Their purpose is to steal information (e.g., login credentials or credit card details). Sometimes, they are used to distribute malware.

More examples of similar scams are "Update/Upgrade On The Messaging Network", "Email Account Disable Request", and "Webmail - Two-Factor Authentication (2FA)".

How do spam campaigns infect computers?

Emails used to spread malware include attachments or links. When these attachments are opened or specific actions are taken, they can infect a device. The files used in such emails can be malicious executables, documents like Word or PDF files, archives, scripts, or other file types.

These messages can also contain links that lead to websites designed to distribute malware. In some cases, simply visiting such a site may trigger an automatic download without any additional user action.

How to avoid installation of malware?

Only download software from trusted sources such as official websites or verified app stores, and avoid pirated programs, cracks, or key generators. Regularly update your operating system and applications to help fix security vulnerabilities.

Be cautious with unsolicited emails or messages, especially when they come from unknown senders. Do not open attachments or click links unless you are sure they are safe. It is also important to avoid suspicious ads, links, and pop-ups on untrusted websites, and never allow notifications from questionable pages.

Text presented in the "Security Check - Mail Delivery Failure Notice" email letter:

Subject: Mail Delivery Failure Notice: Your outgoing messages are being rejected 4/12/2026 9:33:34 a.m.

Security Check Mail Delivery Failure Notice

Attention ********
Your outgoing messages are being rejected

We have detected that emails sent from your account are not reaching some recipients. This may be due to authentication issues or a temporary block.

Affected account: ********
Last failed delivery: 4/12/2026 9:33:34 a.m.
Reason: DMARC / SPF misalignment detected

To restore normal delivery, please verify your account settings by clicking the button below.

Verify Account & Resume Delivery

******** Mail Administrator

© 2026 All Rights Reserved
This notification was generated automatically on 4/12/2026 9:33:34 a.m.. Please do not respond to this message as this mailbox is not monitored.Wm3kLu4

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Fake website used in this scam:

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Quick menu:

• What is Fake Security Check - Mail Delivery Failure Notice?
• Types of malicious emails.
• How to spot a malicious email?
• What to do if you fell for an email scam?

Types of malicious emails:

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.

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 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:

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?

Typically, scammers send identical messages to all recipients. They get email addresses from fake sites, data breaches, or similar sources.

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

If login details are compromised, all related passwords should be changed immediately. If sensitive or financial information is affected, the relevant services, such as banks or providers, should be notified.

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

Malicious files with the .exe extension can infect a device when opened. Infected documents such as PDFs or Word files (and other formats) pose risks depending on how they are interacted with. Whether a device becomes compromised depends on the file type and the user's actions.

I have read the email but did not open the attachment, is my computer infected?

Simply opening a fraudulent email is generally safe. Malware is typically only triggered when a user clicks on links or opens malicious attachments.

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

Combo Cleaner can identify and remove most types of malware. However, some advanced threats may remain hidden within the system and be more difficult to detect. Because of this, performing a full system scan is recommended.