Steve Galloway | Comstat | Ruthin, North Wales

What Is a Shared Mailbox in Microsoft 365 and Why Your Business Should Use One

by Steve Galloway | Oct 4, 2026

What Is a Shared Mailbox in Microsoft 365?

A Microsoft 365 shared mailbox allows multiple users to read and send emails from a common email address, such as support@yourcompany.com or accounts@yourcompany.com. These mailboxes are ideal for teams that need to manage group communications efficiently.

Shared mailboxes do not require a separate Microsoft 365 license, but any user accessing them must have a paid Microsoft 365 license. This makes them a cost-effective solution for collaborative email management.

Click open the headers below to learn more about shared mailboxes. Please read through this entire article before you deal with email account management in Microsoft 365 and associated Exchange Admin Centre (EAC). Be sure to contact us for general advice if you are in doubt. Support options are available for professional assistance.

Why are Shared Mailboxes Useful?

Shared mailboxes offer several practical advantages for businesses:

Team Collaboration: Multiple users can access the same mailbox, making it perfect for departments like support, sales, or accounts.
Offboarding Employees: When an employee leaves, their mailbox can be converted into a shared mailbox to retain access to important communications.
Shared Calendars: Teams can use the shared mailbox calendar to coordinate meetings, deadlines, or events.
File and Folder Sharing: Shared mailboxes can also serve as a central location for storing and accessing shared documents.

Here are some common scenarios where shared mailboxes are great business solutions:

Customer Support Teams: Centralize incoming queries and allow multiple agents to respond.
Accounts Departments: Manage invoices and financial communications from a single address.
Project Teams: Share calendars and documents related to specific projects.
HR Departments: Handle job applications and internal communications securely.

Importantly, a shared email account means colleagues can access an entire email account for the shared email address without having to resort to emails that are forwarded to an individual’s own email account using an email alias. Using an email alias, all incoming email is directed to one principal user’s email account which makes it possible for another user to see all your email.

Creating a Shared Mailbox Without a License

To create a shared mailbox, you don’t need to assign a Microsoft 365 license to the mailbox itself. This is how to do it:

Create a New User in Microsoft 365 Admin Center
1. Go to Users > Active Users and click Add a user
2. Fill in detail field (e.g., name, email address)
  1. Do not assign a license
Convert the User to a Shared Mailbox
1. After creating the user, go to Mailboxes in Exchange Admin Center
2. Select the user and choose Convert to shared mailbox
Assign Permissions
1. Add users who need access by assigning Full Access and Send As permissions.

Using a shared mailbox in this way ideal for setting up departmental mailboxes like info@, sales@, or hr@

Converting an Existing User to a Shared Mailbox After Offboarding

When an employee leaves, their mailbox may contain valuable information. Instead of deleting the account, you can convert it to a shared mailbox:

Convert to a Shared Mailbox
1. Navigate to Exchange Admin Center, select the user’s mailbox, and click Convert to shared mailbox.
Remove the License
1. In the Microsoft 365 Admin Center, remove the user’s license to avoid ongoing costs.
Assign Access to Relevant Team Members
1. Add team members who need access to the mailbox for continuity.
  This approach preserves email history and ensures business continuity without incurring additional licensing fees.

Using a shared mailbox this way preserves email history and ensures business continuity when an employee leaves without incurring additional licensing fees.

Stroage Limits, Archiving, and Compliance

Storage Limits

A shared mailbox without a license has a 50 GB storage limit
If the mailbox exceeds 50 GB, you must assign an Exchange Online Plan 2 license (or equivalent) to increase the limit to 100 GB and enable archiving features

Archiving and Compliance

In-Place Hold or Litigation Hold: If you need to place the mailbox on hold for compliance or legal reasons, a license is required.
Archiving: A shared mailbox can have an archive mailbox, but this feature also requires a license. Without it, archiving isn’t available.
Retention Policies: These can still apply to a shared mailbox, but advanced compliance features often need licensing.

Best Practice

For most departmental or offboarding scenarios, the 50 GB limit is sufficient.
If you anticipate heavy email traffic or need compliance features, keep a license assigned even after conversion.

Summary

Shared mailboxes in Microsoft 365 are a powerful tool for improving team collaboration, managing transitions, and streamlining communication. They are easy to set up and configure, cost-effective, and versatile—making them a smart choice for businesses of all sizes.

About ComStat.uk: Internet Service Provider Comstat provides IT support, web hosting, and media services including website design, Microsoft 365 setup, and audio/video production, serving businesses across Denbighshire, North Wales and Wirral from Ruthin, and Lancashire and the Northwest from Bolton.

Index of articles

by Steve Galloway | Sep 22, 2026

Click open the Index headers below to browse FAQ

Our support articles address the most common issues we deal with “in the field” about Windows, Microsoft 365 Business, web server support, and web design. Click open the accordion sections below to look for self-serve help. Often, issues rely on a knowledge of IT concepts and language. Also, Microsoft, cPanel, and other software houses featured in these articles often update practice notes and procedures without notice. We review our pages regulalry, however you are advised to contact us for further help about these articles especially concerning issues around sovereign account identity and Multifactor Authentication (MFA).

Microsoft Windows 11

Microsoft 365 setup, licensing and user management

Microsoft 365, Exchange Online and Outlook

Microsoft 365 configuration and user tips and tricks

The following articles can be found using <Search> or scrolling through our list of articles. Procedures may have changed since and therefore this content is either being eidted or deprecated. So, although we are editing this content, you might still find useful information to help with issues.

– Exchange Online – room and equipment resources
– Reset Office 365 password expiration policy
– Exchange Email – EOP antivirus/spam
– Exchange Online Protection – EOP
– Microsoft 365 Exchange Email – data leakage & loss protection
– Microsoft ActiveSync

cPanel - web server | email |DNS

cPanel - Sitejet web design software

How to deploy TP-Link Deco with BT Internet Router

by Steve Galloway | Sep 20, 2026

Improving Home Wi-Fi with BT Broadband and TP-Link Deco

If your home has a BT broadband router and two or more TP-Link Deco units, the recommended setup is to use the Deco system to provide all Wi-Fi coverage throughout the property, while the BT router continues to manage the internet connection. TP-Link recommends operating Deco in Access Point (AP) Mode when used alongside an existing router, and Ethernet backhaul is fully supported in this mode.

Click open the headers below to learn how to install a TP-Link Deco WiFi network using your BTInternet router. There are a few methods, one of which replaces the BT router altogether, however we recommend plugging your main Deco unit into your router or connecting via a switch which is plugged into the router. Use Ethernet backhaul in your Tp-Link phone app to interconnect devices using ethernet cabling, or WiFi backhaul if you do not have Ethernet cabling. Support options are available for professional assistance. You can return to our Index of Articles by clicking here.

Recommended Connection Layout for wired Ethernet networks

Where Ethernet cabling is available throughout the property. Firstly, inspect ethernet cabling making sure that plugs and connections are firmly seated. Connect the equipment as follows:

Internet

BT Router

Ethernet Switch (if required)

+————+————+—–

| | |

Deco 1 Deco 2 Deco 3 …etc

Alternatively, all Deco units may be connected directly to the BT router or to a network switch connected to the router.

Why Ethernet Backhaul?

Using Ethernet between Deco units is generally the best-performing option because:

Faster and more reliable than wireless backhau
Less affected by thick walls and interference
Provides better roaming between rooms
Leaves more wireless capacity available for phones, tablets, TVs and laptops

TP-Link specifically supports Ethernet backhaul while operating in Access Point Mode.

Checking That Deco Is Configured in Access Point Mode

Microsoft includes a built-in reset mechanism for the OneDrive client.

Using the TP-Link Deco app on your phone:

Open the Deco app
Select More
Select Advanced
Select Operation Mode (or Operating Mode on some versions)
Confirm that Access Point is selected
If not, select Access Point and save the change
Allow the Deco system to reboot

Finding Advanced settings on TP-Link Deco app

Finding Advanced settings on TP-Link Deco app

Once complete, the Deco system will provide the Wi-Fi service while the BT router continues to perform routing and DHCP functions.

Optional: Disable Wi-Fi on the BT Router

To avoid interference between the BT router and the Deco system, it is usually advisable to turn off the BT router’s own Wi-Fi and use only the Deco Wi-Fi network. Partly, this is because the main Deco unit can be operated as your router instead of your telco supplied router. Also, bandwidth between two operational WiFi networks can cause interruption or disruption. TP-Link also recommends disabling the existing router’s Wi-Fi when using Deco with an existing router.

For most BT Smart Hubs:

Open a web browser
Go to http://192.168.1.254 (this assumes default supplier settings)
Log in to the Hub Manager (you will need your router credentials)
Open Wireless settings
Turn Wi-Fi Off

BT provides these controls through the Hub Manager on supported Hub models.

Next Styeps/If Problems Continue

If your Wi-Fi remains slow, unreliable or does not function correctly after following the above guidance, problems are posible in damaged or improperly cabling pin-outs, misconfigured telco router, poor Deco placement, or possibly broadband connectivity.

Check broadband connectivcity by disengaing all equipment from your router and testing service with a PC or laptop. Introduce device sequentially to check for faulty hardware.

If wired Ethernet backhaul to the router is not providing good service, opt for WiFi backhaul by disconnect remote Decos from cabling, make sure units are in range of main Deco unit. Check settings in your mobile phone app. Then, check WiFi services by grdually moving remote Deco units towards target destinations. Some versions of your phone app include statistics for checking signal performance between Deco units.

If the network is still not operating, professional assistance may be required. On-site diagnosis and remediation can be arranged at my standard call out charge for 90 minutes, and either an hourlyor daily rate, whichever is the lesser.

Comstat provides independent advice on business IT choices that reduce risk, protect continuity, and support long‑term growth. If you need help managhing email, please get in touch, or use our contact page to organize an appointment which suits your timetable. You can return to our Index of Articles by clicking here.

Microsoft OneDrive DLL Error: How to Fix a Corrupted DLL Using a OneDrive Reset

by Steve Galloway | Aug 12, 2026

Microsoft OneDrive DLL Error: How to Fix a Corrupted DLL Using a OneDrive Reset

A client recently reported a startup error on a Windows 11 laptop. The message referenced a corrupted DLL file within the Microsoft OneDrive installation directory:

C:\Users\*user-name*\AppData\Local\Microsoft\OneDrive\Codecs\8.1.2\acutil-60.dll

The error stated that the DLL was either not designed to run on Windows or contained an error. Following additional restart attempts, the client believed Windows itself had become unusable.

Seemingly terminal error messages of this kind are not usually a fatal error message concerning Windows operating system or hardware.

At first glance, this appeared to be a serious operating system failure. However, investigation showed that the issue was most likely a corrupted OneDrive component rather than a broader Windows or hardware problem.

Click open the headers below to learn how to interpret a DLL error message using this case study for repairing a corrupted OneDrive DLL. Support options are available for professional assistance. You can return to our Index of Articles by clicking here.

Understanding the OneDrive DLL Error

DLL files, or Dynamic Link Libraries, contain code and resources used by Windows applications. If one of these files becomes corrupted, Windows may generate a Bad Image error during startup or when launching an application.

A corrupted DLL can occur for several reasons:

Interrupted software updates
File system corruption
Unexpected shutdowns
Third-party security software interference
Storage issues affecting application files

Although the error appeared severe, there was no immediate evidence that Windows itself was damaged.

First Rule: Identify the Application

When you receive a DLL error message, put concern to one side and first determine which application owns the file before taking further action.

In this case, the directory structure clearly indicated Microsoft OneDrive:

C:\Users<username>\AppData\Local\Microsoft\OneDrive

This meant troubleshooting could focus on OneDrive rather than immediately considering a Windows rebuild or hardware replacement.

As a general rule, DLL files found after:

AppData\Local

usually belong to user-installed applications or application components rather than the operating system itself.

The Fix: Reset OneDrive

Microsoft includes a built-in reset mechanism for the OneDrive client.

Using Command prompt, or even by typing <run> in the Windows Search tool on the Windows task bar, this command, the following command can be performed.

%localappdata%\Microsoft\OneDrive\OneDrive.exe /reset

The easiest way to run this command is:

Press Windows + R
Paste the command
Press Enter

Enter Use Windows search to open the utility, and enter the code.

The command stops the OneDrive client, rebuilds local configuration files, clears cached information and restarts the synchronisation engine. Windows may take a minute to execute the reset stages, so we allowed a short while for the computer to process instructions. Depending on your instance of Windows, this command might need modifying. Contact us for help in this case.

In this case, the result was immediate. The client regained normal access to Windows, and the OneDrive DLL error disappeared. This strongly suggested that the underlying problem was a corrupted OneDrive component rather than a damaged Windows installation.

Additional Checks After Fixing the Error

Even when a DLL reset resolves the issue, it is important to verify that deeper corruption does not exist elsewhere.

Open an elevated Command Prompt (use Run in the first instance) and run:

sfc /scannow

System File Checker scans protected Windows files and replaces incorrect versions with known good copies.

If corruption is reported, run:

DISM /Online /Cleanup-Image /RestoreHealth

This command repairs the Windows component store used by System File Checker.

Check the Disk for Problems

Whenever a corrupted DLL is discovered, it is worth checking the storage device for underlying faults.

Run:

chkdsk C: /f

If prompted, schedule the scan for the next restart.

For a more comprehensive examination:

chkdsk C: /f /r

This scans for bad sectors and attempts recovery where possible.

Although the OneDrive reset resolved the immediate issue, disk diagnostics remain an important step because file corruption can sometimes be an early sign of storage problems.

Why This Works for Other Microsoft DLL Problems

This case involved OneDrive, but the same troubleshooting principles apply to many Microsoft applications including:

Outlook
Teams
OneNote
Microsoft 365 Apps
Edge
Windows components

When a DLL error references a file within an application’s own folder structure, a repair, reset or reinstall of that application is often more effective than making direct changes to the DLL itself.

Downloading replacement DLL files from third-party websites is strongly discouraged. These files may not match the installed software version and can introduce security risks.

Instead:

Identify the owning application.
Use the application’s repair or reset function.
Run SFC and DISM if required.
Perform a disk health check.
Reinstall the application only if the problem persists.

Summary

This case demonstrates that not every DLL error indicates a failing computer.

A startup error referencing a corrupted OneDrive DLL initially appeared to be a potentially serious Windows failure. In reality, resetting OneDrive reset restored normal operation within minutes.

For IT professionals and home users alike, the key lesson is straightforward: identify the application responsible for the DLL, use the application’s repair tools first, and then verify overall system health with SFC, DISM and CHKDSK.

In many cases, that approach resolves the issue without requiring a Windows reinstall, profile rebuild or hardware replacement.

Key Takeaway

If you encounter a OneDrive DLL Error, start by resetting OneDrive using:

%localappdata%\Microsoft\OneDrive\OneDrive.exe /reset

Then follow up with SFC, DISM and CHKDSK checks to confirm that the corruption was isolated and not part of a larger storage or operating system issue. This simple process can save hours of troubleshooting and quickly return a Windows PC to normal operation.

Microsoft Entra Passkeys: Why Microsoft Is Retiring SMS Authentication and What You Need to Do

by Steve Galloway | Aug 11, 2026

Why Microsoft Is Retiring SMS Authentication and What You Need to Do

Microsoft Entra Passkeys are being enforced for business users in ealry 2027. This significantly reinforces account security at a time when phishing attacks and malicious intrusion is mushromming. Microsoft-provided SMS and voice authentication for Microsoft Entra ID will retire on 1 February 2027, with passkeys becoming the preferred authentication method.

If you are a Micrsoft 365 tenancy owner you need to be ready for this change. For instance, business owners may need to help staff update their sign-in routine. Recently, some users who only consider themselves Microsoft account holders have received notifications about this as well. This has led to understandable confusion about who is affected and whether any action is required.

The good news is that the change is straightforward once you understand the difference between a Microsoft account and a Microsoft Entra tenant. Also, this article will help you understand how you can determine if you need to action anything if you do not believe you are affected by this.

Click open the headers below to learn more about how Microsoft Entra Passkeys to prepare for Microsoft’s new credential system. Support options are available for professional assistance. You can return to our Index of Articles by clicking here.

What Are Microsoft Entra Passkeys?

A passkey is a modern authentication method designed to replace traditional passwords and SMS verification codes.

Instead of receiving a text message or entering a password, users authenticate using a trusted device such as:

Windows Hello
Face recognition
Fingerprint authentication
A security key
A mobile device linked to the account

Microsoft Entra passkeys are classed as phishing-resistant authentication. This means they are far more difficult for attackers to steal, intercept, or misuse than passwords, voice verification, or SMS codes.

As cybercriminals increasingly rely on phishing campaigns, Microsoft and other major technology companies are moving towards authentication methods that do not depend on passwords or mobile text messages.

Why Is Microsoft Retiring SMS Authentication?

SMS authentication has served organisations well for many years, but it has several weaknesses.

Attackers can:

Trick users into revealing authentication codes
Conduct SIM-swap attacks
Intercept messages in some circumstances
Use social engineering to bypass protections

Passkeys solve many of these problems because authentication occurs directly between the device and Microsoft’s identity platform.

From Microsoft’s point of view, Microsoft Entra passkeys provide a much stronger security baseline for business and organisational accounts. The company is therefore encouraging all affected users to transition before the retirement date.

Who Is Affected?

If you manage a Microsoft 365 Business tenant, Microsoft Entra tenant, Azure subscription, or related cloud services, you should assume that this announcement applies to you.

Even if you already use Microsoft Entra Passkeys using Microsoft Authenticator, you might have some users who still rely on SMS-based multi-factor authentication (MFA). Often, this is because handsets are too old for tools like Microsoft Authenticator to operate on. Those users will need to migrate to a phishing-resistant authentication method before February 2027.

If you only use services such as:

Outlook.com
Hotmail
Xbox
OneDrive Personal
Microsoft 365 Personal
Microsoft 365 Family

you might not be affected.

However, there is an important exception.

Some people created Microsoft cloud services years ago and unknowingly obtained a Microsoft Entra tenant in the background. Microsoft may therefore send administrative notifications to accounts that appear to be ordinary Microsoft accounts.

How to Check If You Have a Microsoft Entra Tenant

If you receive one of these notifications and are unsure whether it applies to you, perform a simple test.

Visit the Microsoft Entra Admin Centre:

Option 1: No Access to a Tenant

If Microsoft reports that you do not have access to a tenant or administrative resources, the notification is unlikely to require any action.

In most cases, personal Microsoft account users can safely disregard the message.

Option 2: Access to a Tenant

If the portal opens and displays tenant information, directory details, or administrative options, Microsoft considers you to have responsibility for an Entra environment.

You should review your authentication methods before the retirement deadline.

Option 3: A Forgotten Trial or Subscription

It is surprisingly common to discover an old Azure trial, Microsoft 365 test tenant, or developer environment that was created years ago.

If one exists, determine whether it is still required. If it remains in use, the transition to Microsoft Entra passkeys should be planned.

What Should You Do?

If you own a Microsoft 365 tenancy, or if your email addressis implicated in Microsoft services listed above which list you in Microsoft Entra, you should begin preparations well before 2027. Recommended actions include:

Review authentication methods currently in use.
Identify users relying solely on SMS or voice authentication.
Check that mobile devices are able to install Microsoft Authenticator app
Enable Microsoft Entra passkeys where appropriate.
Encourage Windows Hello or FIDO2 security key adoption.
Communicate upcoming changes to users.
Test authentication workflows before enforcement begins.

Early adoption reduces the risk of support calls and avoids users being surprised by registration prompts later.

Benefits Beyond Compliance

The move to Microsoft Entra passkeys is not simply another administrative requirement. Identity theft is increasing sinificantly and improved security is not just for business users. In fact, if you are a consumer user and you believe your security is satisfactory even with SMS Authentication, you are in a high risk target group.

Imagine waking up one morning to discover that a malicious party has appropriated control of your online retail and banking accounts, and that they are using your identity to buy expensive luxury watches at auction houses for which payment is intended to be drawn against your savings? If this sounds like fiction, think again. This is just one such situation we have dealt with this year, and the trend is escalating.

Microsoft 365 users enjoy Microsoft Entra ID passkeys that offer:

Better protection against phishing attacks
Reduced password-related support requests
Improved user experience
Faster sign-in processes
Stronger regulatory compliance

In practice, passkeys represent one of the most significant improvements to account security since multi-factor authentication became mainstream. Even if you are not a Microsoft 365 user, we suggest you think very carefully about improving secured access to email. Once an identity is stolen. building a new identity means significant costs and trouble.

Summary

Microsoft Entra passkeys are becoming the future of authentication across Microsoft’s cloud services. While many personal Microsoft account users will not need to take action, anyone responsible for a Microsoft 365 or Entra environment should review their authentication strategy now.

If you receive a notification about the retirement of SMS authentication, the first step is simple: sign in to the Microsoft Entra Admin Centre and determine whether you have access to a tenant. Once you know your status, you can take the appropriate action long before Microsoft’s February 2027 deadline.

Comstat provides independent advice on business IT choices that reduce risk, protect continuity, and support long‑term growth. If you need help with improving your ID security, please get in touch, or use our contact page to organize an appointment which suits your timetable. You can return to our Index of Articles by clicking here .

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