If your business runs on email and Microsoft 365, you know the feeling: something stops working and suddenly nobody can do their job. The reassuring part is that the same handful of problems come up again and again — and most have quick, plain-English fixes. Here are the ones we see most often, what's usually behind them, and how to put each one right.
1. Someone can't sign in
This is the call we get most, and it's almost always one of three things. On a home computer, OneDrive or Office won't sign in because a security setting on that PC is blocking Microsoft-account sign-ins — change that setting, restart, and it works. On a work machine, someone is often signed in with the wrong account, so their email looks empty or their mailboxes seem to have vanished. And for a brand-new hire, the account exists but isn't finished: it needs a Microsoft 365 licence assigned and a first sign-in to activate before email and files appear.
Quick self-checks: confirm which account you're actually signed into (top-right in Outlook or Office), and if a mailbox looks empty, scroll down the folder list on the left — a second mailbox often sits just below the first. If a new starter still can't get in, the licence or first-login step is usually the missing piece.
2. A shared mailbox won't show up
You granted someone access to a shared mailbox — the info@ or accounts@ address the team uses — but it isn't appearing for them. Nine times out of ten the permission is correct and just needs a few minutes to catch up, plus a restart of Outlook to pull it in. If it still hasn't appeared after that, the mailbox usually needs to be added to Outlook by hand. Either way it's a small fix, not a lost mailbox.
3. Your emails are landing in spam — or bouncing
When your own messages end up in customers' spam folders or get rejected outright, the cause is almost always email authentication. Your domain has a set of behind-the-scenes records — SPF, DKIM, and DMARC — that let other mail systems confirm a message really came from you. If those records are missing or misconfigured, receiving servers don't trust your mail, so it gets filtered or refused.
The fix is to set those authentication records up correctly in your domain's DNS. It's a one-time job that quietly protects your deliverability and makes it far harder for anyone to spoof your address. It's exactly the kind of thing we configure when we look after a client's email — if your messages have been vanishing into spam, this is usually why.
4. A suspicious email — or someone already clicked
Phishing is the security problem we see most, and speed matters. If an email asks you to log in, never sign in through the link — go to the site directly. Report obvious phishing in your email app and delete it without opening attachments. If someone has already clicked and entered their password, treat the account as compromised until it's secured: reset the password immediately, turn on two-factor authentication, and check for sign-ins from places the person didn't actually log in from.
If you handle sensitive or client information, this matters even more — a single compromised mailbox can expose a lot. The good habit to build across your team: when an unexpected email, attachment, or login request turns up, forward it to whoever handles your IT before touching it, rather than opening it to find out.
5. When 'low disk space' doesn't add up
A computer warning about low disk space when you know there's room free is often OneDrive busily syncing large files to the cloud. Turning on Files On-Demand keeps those files available online without filling the local drive, and moving big archives to the cloud frees up space for good. If a machine is genuinely full — common on small tablets and 2-in-1s that can't be upgraded — the answer is usually cloud storage rather than a new device.
| What you see | What's usually going on |
|---|---|
| Can't sign in to OneDrive/Office on a home PC | A security setting on that PC is blocking Microsoft-account sign-ins — change it and restart |
| A shared mailbox won't appear | The permission is still catching up — give it a few minutes and restart Outlook |
| Your emails go to spam or bounce | Missing or wrong email authentication (SPF/DKIM/DMARC) in your DNS |
| An email asking you to log in | Assume phishing — go to the site directly, never the link, then report and delete |
| 'Low disk space' but space is free | OneDrive is syncing large files — turn on Files On-Demand |
Notice the pattern: almost none of these are dramatic failures. They're settings, permissions, and security housekeeping — the sort of thing that quietly goes wrong and quietly gets fixed. That's also why they rarely surprise a business that has someone keeping an eye on it: proactive IT support catches most of this before you notice, and turns the rest into a quick call instead of a lost morning.