Microsoft 365 Common Problems for Small Businesses

Microsoft 365 is the backbone of most small business operations — email, files, Teams calls, shared calendars. When it goes wrong, it affects everyone. These are the five most common M365 issues we see in small business teams across London, and what usually causes them.

1. Email going to recipients' spam folders

Business email ending up in spam is more common than it should be, and it usually points to DNS configuration rather than anything wrong with the email content. The key records are SPF (which authorises your domain to send mail), DKIM (which cryptographically signs each message), and DMARC (which tells receiving servers what to do with mail that fails those checks). If any of these are missing or incorrectly configured, your email looks suspicious to receiving mail servers — even though it's legitimate.

The fix involves updating your domain's DNS records. It's a straightforward task but requires access to your domain registrar and an understanding of the correct values for Microsoft 365.

2. OneDrive sync errors and conflicts

OneDrive sync errors are a regular source of frustration. Files get stuck, show conflict copies, or stop syncing entirely. Common causes include file path lengths exceeding Windows limits, files with unsupported characters in the name, storage quota being reached, or the OneDrive client needing to be reset. In shared library scenarios, multiple people editing the same file simultaneously can also create conflicts.

Quick checks to try:

• Check the OneDrive system tray icon for error messages — it usually tells you exactly which file is causing the problem.
• Check available storage in your M365 account.
• Look for files with very long names or special characters and rename them.
• Reset the OneDrive client if errors persist after the above.

3. Teams audio and video issues

Teams calls with broken audio, one-way audio, or no video are among the most commonly reported M365 problems. The causes are usually device-level rather than network-level — wrong microphone or camera selected in Teams settings, a browser-based Teams session conflicting with the desktop app, or audio drivers that need updating. In some cases, it's a Bluetooth headset that hasn't connected properly.

Check Teams settings (device settings inside a call) to confirm the correct audio inputs and outputs are selected. If problems are consistent for one person, the issue is with their device setup rather than the organisation's Teams configuration.

4. Licence management getting out of control

Small businesses without dedicated IT often lose track of their Microsoft 365 licences. Staff leave but accounts aren't removed. New starters get set up quickly but with the wrong licence type. Licences pile up and costs rise without anyone noticing. In some cases, former employees retain access to business email and files for months after leaving.

A quarterly review of active M365 users and licence assignments takes around twenty minutes and prevents this from becoming a problem. Removing a departed employee's account promptly also closes a significant security gap.

5. Password resets and MFA lock-outs

When multi-factor authentication is enabled — which it should be — there are more ways for a user to get locked out. Lost phone, new phone not set up for MFA, authenticator app not synced. These situations need an admin to reset the MFA registration for the affected account.

The fix is quick once you know where to find it in the Microsoft 365 admin centre. The problem is that small businesses often don't have someone who knows how to do this — which is why password resets and MFA lock-outs are one of the most common M365 support requests we receive.