Roundcube Mailbox Is Almost Full Email Scam Steals Your Login Password
Written by: Lapain Epuran
Published on:
A Roundcube alert says your mailbox has used 1,993 MB of a 2,000 MB quota. With incoming messages supposedly about to stop, the Clean Up Mailbox button feels like the quickest way to keep email working.
The Roundcube Mailbox Is Almost Full email scam does not open a storage-management page. Its button leads to rehierl[.]de, where a copied Roundcube sign-in form asks for the mailbox password.
The page may already know the victim's email address because it was placed in the link. A prefilled username can look like proof that the alert came from the provider, but it is simply information the attacker already had.
Roundcube is legitimate open-source webmail software, not a universal email provider. The Roundcube project does not manage individual mailboxes or send users account-suspension and password-verification notices.
Overview
The storage figures create a believable emergency
The message says the mailbox has reached 1,993 MB, more than the 90% warning threshold of a 2,000 MB quota. It warns that new mail may stop arriving when the limit is reached.
Those figures are specific enough to resemble an automatic system report. They are not taken from the recipient's actual server and should be compared with the quota displayed inside webmail reached independently.
The cleanup button leaves the real mail server
The button reads Open Roundcube & Clean Up Mailbox. It does not lead to the organization's normal webmail address or a storage page operated by the email host.
Instead, the documented campaign opens rehierl[.]de. A page on that unrelated domain can copy Roundcube's logo and layout, but it cannot become the trusted login supplied by the recipient's provider.
The supposed cleanup is credential theft
The destination shows a Roundcube-style login with the email address prefilled. The user is asked to enter the current password before messages can supposedly be deleted or incoming delivery restored.
Any password entered can be sent directly to the attacker. No storage is freed, and the captured mailbox may be used to read private mail, reset connected accounts, and impersonate the owner.
The subject says Mailbox storage full.
The alert claims 1,993 MB of a 2,000 MB quota is already used.
A 90% threshold is shown to make the figures look automated.
The message warns that incoming email may stop.
Open Roundcube & Clean Up Mailbox leads away from the real host.
The destination is rehierl[.]de.
A fake Roundcube page prefills the victim's email address.
The form collects the current mailbox password instead of cleaning storage.
Why a Nearly Full Mailbox Warning Feels So Credible
Real mail systems do enforce storage quotas. Large attachments, years of sent mail, deleted items, and spam can fill an account, so a capacity warning fits a problem many users have seen before.
The scam also describes a realistic consequence. Once a server-side quota is exhausted, mail can be delayed or rejected. A user expecting an invoice, password reset, or customer reply may feel unable to wait.
Specific numbers strengthen the illusion. The difference between 1,993 MB and 2,000 MB leaves only 7 MB, which makes the invented deadline feel immediate without requiring an explicit countdown.
Roundcube branding works because many hosting companies install the same software. Users may recognize the interface but not know the exact organization responsible for their account, support, storage, or login URL.
That uncertainty is precisely what the campaign exploits. The victim recognizes Roundcube and assumes the project itself sent the notice, even though the mailbox is actually operated by a hosting provider, employer, school, or internet service provider.
What Roundcube's Own Guidance Establishes
Roundcube describes itself as a browser-based IMAP client. It is software that a mail operator installs, not a public email service that creates and manages every user's account.
The Roundcube project explicitly warns about phishing emails that pretend to come from Roundcube Webmail and ask users to enter an email password on fake sites. It says users do not have an account with the Roundcube project itself.
Official Roundcube help tells users to open the webmail URL supplied by their system administrator. That trusted address varies by organization, which is why an unexpected cleanup button cannot establish the correct destination.
A genuine quota problem can be checked after signing in through the known webmail address. The storage meter, folder sizes, Trash, Junk, and administrator controls should provide the same information without routing through rehierl[.]de.
No malware download was confirmed in this campaign. The verified purpose is phishing, so the most important event is entering credentials. A device scan becomes relevant if the site downloaded a file or requested software.
How the Roundcube Mailbox Is Almost Full Email Scam Works
Step 1: A fake storage notification reaches the inbox
The message presents itself as an automated Roundcube alert. A familiar orange or blue webmail logo, a system-style sender name, and a no-reply footer make it look generated by the server.
The display name is not proof of origin. The actual sender domain, authentication results, and a matching notice inside the independently opened account carry more weight.
Step 2: Precise quota figures create urgency
The email claims that 1,993 MB of 2,000 MB has been used and that the 90% warning threshold was crossed. The victim appears to have almost no room left.
Because the figures sound technical, recipients may not question where they came from. The attacker does not need access to the real mailbox to place numbers in an HTML email.
Step 3: The message threatens incoming delivery
The warning says the account may no longer receive new messages at the maximum quota. This turns a maintenance task into a threat to work, billing, recovery codes, and personal communication.
A real provider may send capacity warnings, but the user can verify them through the normal portal. The consequence does not validate the route offered by the email.
Step 4: The cleanup button opens rehierl[.]de
Open Roundcube & Clean Up Mailbox appears to be a direct maintenance shortcut. The actual link leaves the organization's known server and loads an unrelated domain controlled or abused by the campaign.
A lock icon only means the connection to that domain is encrypted. It does not prove the site belongs to the provider or Roundcube.
Step 5: The fake page prefills the email address
The phishing link can carry the target address as a parameter. The page reads it and places it into the username field before the victim types anything.
This personalization is not a live account lookup. The attacker already needed the address to deliver the phishing email and can reuse it on the destination page.
Step 6: The password is captured
The visitor enters the mailbox password to continue. The form can transmit it immediately, then show an error, request another attempt, or redirect to genuine webmail.
A second prompt may collect a corrected or alternate password. A final redirect can make the victim believe the cleanup succeeded or that the alert was merely buggy.
Step 7: The mailbox becomes an attack platform
Criminals can search messages, steal contacts, reset other accounts, and learn how the owner communicates. Unknown forwarding rules can keep future mail flowing to the attacker.
Messages sent from the real account are more convincing than ordinary spam. Colleagues, customers, friends, and suppliers may trust a follow-up link or payment request because it arrives from a familiar address.
Company and Checkout Checks
Use the webmail URL supplied by the administrator
Open the saved address used every day or ask the hosting provider, employer, school, or internet service provider for the correct Roundcube URL. Do not discover it through the warning email.
The legitimate login may use a custom company domain and branding because Roundcube is installed by many different operators. rehierl[.]de is not made trustworthy by displaying the generic interface.
Check the real quota after a trusted login
Review the storage meter, account dashboard, folder sizes, and hosting control panel. Delete messages only after verifying that the quota is genuinely close to its limit.
Emptying Trash and Junk can free real space, but it can be done inside the authenticated mailbox. A cleanup process should not require re-entering the password on an unrelated site.
Contact the organization that actually runs the mailbox
Roundcube's project team cannot reset a hosted user's password or change an individual quota. Those responsibilities belong to the mail host or local administrator.
Use a known support portal or telephone number. Do not reply to the alert, because an attacker-controlled reply address cannot independently confirm its own claim.
Let the password manager check the domain
A password manager normally offers Roundcube credentials only on the saved host. If it refuses to autofill on rehierl[.]de, treat that as a security warning.
Do not work around the mismatch by typing manually. Verify the domain first, because copied logos and prefilled usernames are easy for a phishing kit to reproduce.
Warning Signs to Check Before You Act
An unsolicited message says the mailbox is almost exactly full.
The figures claim 1,993 MB of 2,000 MB is used.
A 90% threshold conflicts with the displayed 99.6% usage.
Incoming mail is threatened unless the user acts through one button.
The sender acts as if Roundcube itself manages the account.
The cleanup link leads to rehierl[.]de.
The destination does not match the normal webmail host.
A login appears before any message-deletion controls.
The page prefills the email address carried in the URL.
The current password is requested on an unrelated domain.
No matching quota warning appears inside the real account.
The real hosting provider or administrator cannot confirm the notice.
The quota story may describe a real kind of problem, but it does not prove this alert is real. The decisive evidence is the destination: a Roundcube password belongs only on the webmail host supplied by the organization running the account, never on rehierl[.]de.
What to Do if You Have Fallen Victim to This Scam
Change the exposed password immediately. Open your hosting provider's real Roundcube webmail URL through a saved bookmark or its official application, not through the Roundcube mailbox-full message. Create a strong, unique password and replace it anywhere the same or a similar password was reused.
Enable stronger multi-factor authentication. Prefer a passkey, hardware security key, or authenticator app when available. Review the methods already registered and remove telephone numbers, recovery addresses, app passwords, or security keys you do not recognize.
Revoke active sessions and connected applications. Sign out other sessions and inspect OAuth access, browser sessions, mail clients, and third-party applications. A criminal may retain access through an issued token even after the primary password has changed.
Inspect mailbox rules and forwarding settings. Remove unknown forwarding addresses, delegates, filters, automatic replies, and rules that hide security messages. Review sent mail, trash, deleted messages, and account-recovery notifications for activity you did not initiate.
Secure accounts that use the mailbox for recovery. Prioritize banking, payment services, cloud storage, shopping, social media, workplace tools, and password managers. Change credentials wherever the compromised inbox could receive a reset link or approval request.
Protect the service impersonated by the email. Review mailbox storage, active sessions, and hosting-account settings through its official account and contact support through a verified channel. Remove unknown addresses, payment methods, documents, devices, or profile changes associated with the scam's story.
Scan the device if anything was downloaded. Run a complete scan with Malwarebytes or another trusted security product if the page delivered a file, browser extension, or remote-support tool. Remove unfamiliar software and install operating-system and browser updates.
Add a blocking layer for future attempts. AdGuard or another reputable DNS and content blocker can stop some known phishing pages and malicious advertising from loading. Continue checking addresses because new campaign domains may appear before blocklists update.
Report the phishing message. Use the mail provider's Report Phishing control and notify your email host, workplace administrator, or internet service provider. Preserve the full message and headers first, especially if multiple employees or customers received the same lure.
Warn contacts if the account was misused. Contact colleagues, customers, friends, and vendors through another channel. Ask them to ignore recent links, password requests, file shares, shipment notices, or payment instructions sent during the possible compromise window.
Reject unsolicited recovery offers. A caller or email sender who promises to recover the account or lost money for an advance payment may be extending the fraud. Work only with the provider, financial institution, employer, police, or a verified incident-response professional.
Is Your Device Infected? Run a Free Malware Scan
Slow performance, constant pop-ups, or strange behavior? These are classic signs of a malware infection. The fastest way to find out is to scan your device with Malwarebytes Anti-Malware Free — one of the most trusted malware removal tools available.
The free version detects and removes the most common threats, including:
Adware — the cause of those annoying pop-ups
Browser hijackers — unwanted redirects and changed homepages
Trojans and spyware — hidden programs stealing your data
Potentially unwanted programs (PUPs) — software you never asked for
👉 Select your device below — Windows, Mac, or Android — then follow the simple steps to download Malwarebytes, scan your system, and remove any threats it finds. The whole process takes about 5 minutes.
Malwarebytes for WindowsMalwarebytes for MacMalwarebytes for Android
Run a Malware Scan with Malwarebytes for Windows
Malwarebytes is one of the most popular and trusted anti-malware tools for Windows — and it’s completely free for removing infections. It catches threats that many antivirus programs miss, including adware, browser hijackers, and trojans. Follow the steps below to scan and clean your PC in just a few minutes.
Download Malwarebytes
Click the button below to download the latest version of Malwarebytes for Windows from the official source. The free version is all you need — it will scan your computer and remove adware, browser hijackers, and other malicious software at no cost.
(The link opens in a new page where your download will start)
Install Malwarebytes
When the download finishes, open your Downloads folder and double-click the MBSetup file. If Windows shows a User Account Control pop-up, click “Yes” to allow the installation.
Follow the On-Screen Prompts to Install Malwarebytes
The setup wizard will walk you through a few quick screens:
Choose where you’re installing the program — “Personal Computer” or “Work Computer” — then click Next.
Malwarebytes will now install on your device. This usually takes under a minute.
When installation is complete, the “Welcome to Malwarebytes” screen will open automatically.
On the final screen, click Open Malwarebytes to launch the program.
Enable “Scan for Rootkits”
Before scanning, turn on rootkit detection so Malwarebytes can find even the most hidden threats. Click the Settings gear icon on the left side of the screen.
In the settings menu, find “Scan for rootkits” and click the toggle so it turns blue.
Done? Click “Dashboard” in the left pane to return to the main screen.
Start the Scan
Click the blue Scan button. Malwarebytes will automatically update its virus database and start checking your computer for malware.
Wait for the Scan to Finish
The scan checks your entire system for browser hijackers and other malicious programs, so it can take several minutes. Feel free to do something else — just check back occasionally to see the progress.
Quarantine the Detected Threats
When the scan is done, you’ll see a list of everything Malwarebytes found — malware, adware, and potentially unwanted programs. Click the “Quarantine” button to remove all of them at once.
Malwarebytes will now remove the malicious files and registry entries and move them safely into quarantine.
Restart Your Computer
Some threats can only be fully removed after a reboot. If Malwarebytes asks you to restart, click Yes. Once you’re logged back in, your PC is clean and you can continue with the next steps in this guide.
When the scan finishes, click Quarantine to remove everything Malwarebytes found. That’s it — your Windows PC is now clean of trojans, adware, and other malware, and should be back to running smoothly.
If your current antivirus allowed this malicious program on your computer, you may want to consider purchasing Malwarebytes Premium to protect against these types of threats in the future. If you are still having problems with your computer after completing these instructions, then please follow one of the steps:
Malwarebytes for Mac is a free on-demand scanner that removes the malware other security software tends to miss — adware, browser hijackers, and unwanted programs included. Cleaning an infected Mac with Malwarebytes has always been completely free, and it’s our go-to recommendation. Follow the steps below to scan and clean your Mac in just a few minutes.
Download Malwarebytes for Mac
Click the button below to download the latest version of Malwarebytes for Mac.
When the download finishes, open your Downloads folder and double-click the setup file to begin the installation.
Follow the On-Screen Prompts to Install Malwarebytes
The Malwarebytes for Mac Installer will guide you through a few quick screens. Click “Continue” and keep following the prompts until the installation completes.
When the installation is complete, Malwarebytes opens to the Welcome to Malwarebytes screen. Click “Get started“.
Select “Personal Computer” or “Work Computer”
Malwarebytes will ask what type of computer you’re installing it on. Click either Personal Computer or Work Computer, whichever applies.
Start the Scan
Click the “Scan” button. Malwarebytes will automatically update its detection database and begin checking your Mac for malware.
Wait for the Scan to Finish
Malwarebytes will scan your Mac for adware, browser hijackers, and other malicious programs. This can take a few minutes, so feel free to do something else — just check back occasionally to see the progress.
Quarantine the Detected Threats
When the scan is done, you’ll see a list of everything Malwarebytes found. Click the “Quarantine” button to remove all the threats at once.
Restart Your Mac
Malwarebytes will now remove all the malicious files it found. Some threats can only be fully removed after a reboot — if Malwarebytes asks you to restart, allow it. Once you’re logged back in, your Mac is clean.
Once the scan is done, remove every threat it detected. Your Mac is now free of adware, rogue browser extensions, and other potentially harmful software.
If your current antivirus allowed a malicious program on your computer, you might want to consider purchasing the full-featured version of Malwarebytes Anti-Malware to protect against these types of threats in the future. If you are still experiencing problems while trying to remove a malicious program from your computer, please ask for help in our Mac Malware Removal Help & Support forum.
Run a Malware Scan with Malwarebytes for Android
Malwarebytes for Android automatically detects and removes dangerous threats like malware and ransomware so you don’t have to worry about your most-used device being compromised. Aggressive detection of adware and potentially unwanted programs keeps your Android phone or tablet running smooth.
Download Malwarebytes for Android.
You can download Malwarebytes for Android by clicking the link below.
In the Google Play Store, tap “Install” to install Malwarebytes for Android on your device.
When the installation process has finished, tap “Open” to begin using Malwarebytes for Android. You can also open Malwarebytes by tapping on its icon in your phone menu or home screen.
Follow the on-screen prompts to complete the setup process
When Malwarebytes will open, you will see the Malwarebytes Setup Wizard which will guide you through a series of permissions and other setup options. This is the first of two screens that explain the difference between the Premium and Free versions. Swipe this screen to continue. Tap on “Got it” to proceed to the next step. Malwarebytes for Android will now ask for a set of permissions that are required to scan your device and protect it from malware. Tap on “Give permission” to continue. Tap on “Allow” to permit Malwarebytes to access the files on your phone.
Update database and run a scan with Malwarebytes for Android
You will now be prompted to update the Malwarebytes database and run a full system scan.
Click on “Update database” to update the Malwarebytes for Android definitions to the latest version, then click on “Run full scan” to perform a system scan.
Wait for the Malwarebytes scan to complete.
Malwarebytes will now start scanning your phone for adware and other malicious apps. This process can take a few minutes, so we suggest you do something else and periodically check on the status of the scan to see when it is finished.
Click on “Remove Selected”.
When the scan has been completed, you will be presented with a screen showing the malware infections that Malwarebytes for Android has detected. To remove the malicious apps that Malwarebytes has found, tap on the “Remove Selected” button.
Restart your phone.
Malwarebytes for Android will now remove all the malicious apps that it has found. To complete the malware removal process, Malwarebytes may ask you to restart your device.
After the scan, tap Remove Selected to delete all detected threats. Your Android phone is now clean — no more malicious apps, adware, or browser redirects.
If your current antivirus allowed a malicious app on your phone, you may want to consider purchasing the full-featured version of Malwarebytes to protect against these types of threats in the future. If you are still having problems with your phone after completing these instructions, then please follow one of the steps:
Restore your phone to factory settings by going to Settings > General management > Reset > Factory data reset.
Now that your device is clean, keep it that way. Most infections start with a malicious ad or a fake download button — so blocking them at the source is your best defense.
We recommend AdGuard, which blocks malicious ads, phishing pages, and dangerous redirects before they can reach you.
No. The documented campaign uses fake quota figures and a copied Roundcube login on rehierl[.]de to steal mailbox credentials.
Can a real Roundcube mailbox become full?
Yes. Storage quotas are controlled by the mail host, but the status should be checked inside the known webmail or hosting portal, not through an unexpected email link.
Why was my email address already filled in?
The address can be placed inside the phishing URL and copied into the form. That personalization does not show that the page accessed your real account.
Does Roundcube send storage and suspension emails?
Roundcube is software, not the provider managing your mailbox. The Roundcube project warns that it does not send users messages asking them to enter an email password.
What if I clicked but entered no password?
Close the page, report the message, and review browser downloads. If no credential was submitted and nothing was installed, account takeover is less likely.
What if I entered my password?
Change it immediately through the real host, revoke sessions, enable stronger authentication, inspect forwarding rules, and secure every account that uses the mailbox for recovery.
The Bottom Line
The Roundcube Mailbox Is Almost Full email scam turns a believable storage problem into a password trap. Its precise 1,993 MB figure, 90% threshold, and prefilled username are designed to make rehierl[.]de feel like part of the mail system.
Roundcube is the software interface, not the organization responsible for the account. Check capacity through the webmail URL supplied by the real host and contact that host for support.
If the password was entered, treat the mailbox as compromised. Change credentials, revoke sessions, inspect forwarding, secure recovery accounts, and warn contacts before the inbox is used to send the next phishing message.
10 Rules to Avoid Online Scams
Here are 10 practical safety rules to help you avoid malware, online shopping scams, crypto scams, and other online fraud. Each tip includes a quick “if you already got hit” action.
Stop and verify before you click, log in, download, or pay.
Most scams win by creating urgency. Verify using a trusted method: type the website address yourself, use the official app, or call a known number (not the one in the message).
If you already clicked: close the page, do not enter passwords, and run a malware scan.
Keep your operating system, browser, and apps updated.
Updates patch security holes used by malware and malicious ads. Turn on automatic updates where possible.
If you saw a scary “update now” pop-up: close it and update only through your device settings or the official app store.
Use layered protection: antivirus plus an ad blocker.
Antivirus helps block malware. An ad blocker reduces scam redirects, phishing pages, and malvertising.
If your browser is acting weird: remove unknown extensions, reset the browser, then run a full scan.
Install apps, software, and extensions only from official sources.
Avoid cracked software, “keygens,” and random downloads. During installs, choose Custom/Advanced and decline bundled offers you do not recognize.
If you already installed something suspicious: uninstall it, restart, and scan again.
Treat links and attachments as untrusted by default.
Phishing often impersonates delivery services, banks, and popular brands. If it is unexpected, do not open attachments or log in through the message.
If you entered credentials: change the password immediately and enable 2FA.
Shop safely: research the store, then pay with protection.
Be cautious with brand-new stores, “closing sale” stories, and prices that make no sense. Prefer credit cards or PayPal for dispute options. Avoid wire transfers, gift cards, and crypto payments.
If you already paid: contact your card issuer or PayPal quickly to dispute the transaction.
Crypto rule: never pay a “fee” to withdraw or recover money.
Common patterns include fake profits, then “tax,” “gas,” or “verification” fees. Another is a “recovery agent” who demands upfront crypto.
If you already sent crypto: stop paying, save evidence (wallet addresses, TXIDs, chats), and report the scam to the platform used.
Secure your accounts with unique passwords and 2FA (start with email).
Use a password manager and unique passwords for every account. Enable 2FA using an authenticator app when possible.
If you suspect an account takeover: change passwords, sign out of all devices, and review recent logins and recovery settings.
Back up important files and keep one backup offline.
Backups protect you from ransomware and device failure. Keep at least one backup on an external drive that is not always connected.
If you suspect infection: do not connect backup drives until the system is clean.
If you think you are a victim: stop losses, document evidence, and escalate fast.
Move quickly. Speed matters for disputes, account recovery, and limiting damage.
Stop payments and contact: do not send more money or respond to the scammer.
Call your bank or card issuer: block transactions, replace the card if needed, and start a dispute or chargeback.
Secure your email first: change the email password, enable 2FA, and remove unfamiliar recovery options.
Secure other accounts: change passwords, enable 2FA, and log out of all sessions.
Scan your device: remove suspicious apps or extensions, then run a full malware scan.
Save evidence: screenshots, emails, order pages, tracking pages, wallet addresses, TXIDs, and chat logs.
Report it: to the payment provider, marketplace, social platform, exchange, or wallet service involved.
These rules are intentionally simple. Most online losses happen when decisions are rushed. Slow down, verify independently, and use payment methods and account controls that give you recourse.
Hello! I'm Lapain Epuran, your go-to source for detailed and honest product reviews. From tech gadgets to miracle cures, I provide insights to help you make informed choices. Join me as we discover what's truly worth your time and money.
