How to identify fake "Mail Server Authentication Unsuccessful" emails

What kind of email is "Mail Server Authentication Unsuccessful"?

After examining this "Mail Server Authentication Unsuccessful" email, we determined that it is spam. It claims that an error has occurred, disrupting the mail service authentication process. This spam campaign aims to trick recipients into visiting a phishing site targeting email account log-in credentials.

"Mail Server Authentication Unsuccessful" email scam overview

The spam email with the subject "Important: Mail Server Configuration Alert" (may vary) is presented as an alert concerning an authentication connection issue. Specifically, the mail server authentication was unsuccessful. The message details the error that has caused this, and warns that it may cause email service issues.

It must be emphasized that the information in this message is false, and this mail is not associated with any legitimate service providers.

Pressing the "Refresh Webmail" button results in a redirect to a phishing website disguised as an email account sign-in page. Hence, attempts to sign in through this webpage expose the email account to scammers.

Emails can be variously abused; they tend to contain incredibly sensitive data and may open an avenue for stealing connected accounts, platforms, or services (e.g., social networking/media, messengers, e-commerce, entertainment, online banking, digital wallets, etc.).

Scammers can steal the account owner's identity and ask for loans or donations from contacts/friends/followers, endorse scams, and spread malware by sharing malicious links or files. Stolen finance-related accounts can be used to make fraudulent transactions and online purchases.

In summary, by trusting an email like "Mail Server Authentication Unsuccessful" – users can experience severe privacy issues, financial losses, and identity theft.

If you have already entered your log-in credentials into a phishing website/file – immediately change the passwords of all possibly compromised accounts and contact their official support.

Phishing spam campaign examples

"Pending Mails Alert", "Security Alert - We've Detected Trojan Malware", and "Your Account Access Needs Reconfirmation" are just a couple of our newest articles on phishing campaigns.

Log-in credentials are not the only type of data targeted by these emails; personally identifiable details and finance-related information are common targets as well. Various scams are promoted through spam mail, and it is used in malware distribution.

Due to how prevalent this mail is and how well-made it can be – we strongly advise exercising caution with incoming emails, DMs/PMs, SMSes, and other messages.

How do spam campaigns infect computers?

Spam campaigns proliferate malware by distributing infectious files as attachments or download links. These files come in various formats, e.g., documents (Microsoft Office, Microsoft OneNote, PDF, etc.), archives (ZIP, RAR, etc.), executables (EXE, RUN, etc.), JavaScript, and so on.

Merely opening a malicious file can be enough to initiate the infection chain. However, some formats need additional user interaction to trigger malware infiltration processes. For example, Microsoft Office files require users to enable macro commands (i.e., editing/content), while OneNote documents need them to click on embedded links or files.

How to avoid installation of malware?

We highly recommend vigilance with incoming emails and other messages. Attachments or links found in dubious/irrelevant communications must not be opened, as they can be harmful or virulent.

However, malware is not spread exclusively through spam campaigns. Therefore, we advise being careful while browsing since the Internet is full of deceptive and malicious content.

Additionally, all downloads must be made from official and verified channels. Software must be activated and updated using functions/tools provided by legitimate developers, as illegal product activation ("cracking") tools and third-party updates can contain malware.

We must stress the importance of having a reputable antivirus installed and kept updated. Security programs must be used to perform regular system scans and to remove active and potential threats. 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 "Mail Server Authentication Unsuccessful" spam email letter:

Subject: Important: Mail Server Configuration Alert

******** Authentication Connection Issue

Mail Server authentication unsuccessful

Missing SSL/TLS Configuration (Recommended)
Username: ********
Password: Use email account password
Incoming Server Error: IMAP Port: 993 POP3 Port: 995
Outgoing Server Error: SMTP Port: 465
Important: Immediate action required to maintain deliverability

Refresh Webmail

This notice was generated on 9/24/2025
Login to webmail to refresh

Copyright© 2025 cPanel, L.L.C.

Screenshot of the phishing website promoted by the "Mail Server Authentication Unsuccessful" spam campaign:

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Quick menu:

• What is "Mail Server Authentication Unsuccessful" phishing email?
• 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?

Spam emails are not personal, regardless of any relevant information that they may include. These emails are sent out in large-scale operations – therefore, thousands of users receive identical or incredibly similar messages.

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

If you have provided your log-in credentials – change the passwords of all potentially exposed accounts and inform their official support without delay. However, if you have disclosed information of a different personal nature (e.g., passport photos/scans, credit/debit card numbers, etc.) – immediately contact the appropriate authorities.

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

No, reading an email does not pose an infection threat. Devices are compromised when malicious attachments or links are opened/clicked.

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

If the opened file was an executable (.exe, .run, etc.) – most likely, yes – the system was infected. However, you might have avoided this if it was a document (.doc, .xls, .pdf, .one, etc.). These formats may need additional actions (e.g., enabling macros, clicking embedded files/links, etc.) to jumpstart malware download/installation processes.

Will Combo Cleaner remove malware infections present in email attachments?

Yes, Combo Cleaner can detect and remove almost all known malware infections. It must be emphasized that high-end malicious software usually hides deep with systems – therefore, running a full system scan is essential.