What Was Happening
A customer in Putney SW15 asked us out for help with Microsoft 365 and a few other things that had built up. The main complaint was Outlook.
It kept asking for the password. They would enter it — correctly — and the prompt would go away and then reappear. Sometimes immediately, sometimes after a few minutes. Alongside that, mail had stopped syncing properly: new messages weren’t arriving reliably, and things sent from the phone weren’t showing up on the computer as they should.
This is one of the most quietly maddening faults in everyday computing, because the software is asking a question the user can answer, they are answering it correctly, and it makes no difference. The natural conclusion is that something is wrong with the password. It almost never is.
Sound like your problem?
Bring it to our Putney workshop or message us a photo and we will give you a straight answer and a quote before any work starts.
Our Diagnosis
The important thing to establish first is what a repeated password prompt actually means, because the wording misleads people.
Outlook doesn’t hold your password and check it locally. It uses a stored sign-in token obtained from Microsoft when the account was first set up — a credential that proves the account is authorised, kept in Windows’ credential store and renewed quietly in the background. Outlook prompts when it can’t connect using what it has.
So the prompt says “enter your password”, but the real message is “the stored sign-in isn’t being accepted”. Those are different problems, and the second one isn’t fixed by typing the password again. In fact typing it again often changes nothing at all, because the new entry is being layered on top of a stored credential that’s still invalid — which is exactly the loop this customer was in.
That also explains the sync symptom. Mail not updating and the password prompt weren’t two separate faults; they were the same fault seen from two angles. Outlook couldn’t authenticate, so it couldn’t connect, so nothing synchronised — and each failed attempt produced another prompt.
What breaks a stored sign-in is usually a change somewhere else entirely: a password changed on another device or via a web browser, the account being enrolled in multi-factor authentication, a security policy applied to the account, or simply a stored credential going stale and failing to renew. From the user’s point of view nothing was done to the computer, which is why the fault seems to come from nowhere.
Before doing anything to the account we ruled out the simpler explanations — that the machine had a working internet connection, and that this was specific to the mail account rather than a general connectivity problem. Both checked out, which confirmed the fault sat with the account’s authentication rather than the machine or the line.
How We Fixed It
The fix was to break the loop rather than feed it.
We cleared the stale stored sign-in for the account, so that Outlook no longer had an invalid credential to keep retrying. That step is the one that matters, and it’s the one most people never get to, because nothing in the prompt suggests that a saved credential exists or that it might be the problem.
With the old credential removed we re-authenticated the account against Microsoft 365 properly, letting it complete the full sign-in and issue a fresh, valid token — including any additional verification the account now required.
Then we let the mailbox synchronise fully and watched it rather than assuming. A mailbox that has been failing to sync for a while has catching up to do, and the meaningful test is whether it completes and stays connected, not whether the prompt disappeared for a minute. Outlook connected cleanly, stopped prompting, and mail came through normally.
We also picked up the other bits and pieces the customer had accumulated while we were there, which is generally the most efficient way to use an onsite hour — the small unresolved things tend to be quick once someone is sitting at the machine.
The Result
Outlook connected without prompting and mail synced normally again, sorted within the hour booked.
We explained what had actually happened, which matters more than it might seem. A customer who understands that the prompt meant “the saved sign-in expired” rather than “you typed your password wrong” is far better placed the next time something similar happens — and much less likely to spend an evening trying passwords.
Why This Happens
Email authentication has changed considerably over the last few years, and this fault is largely a side effect of that change.
Mail clients used to work in a simple way: they stored your password and sent it each time they connected. That was easy to understand and not very secure — the password sat on the device, and anyone who obtained it had complete access. Microsoft 365 and other modern services replaced this with token-based sign-in, where the app receives a time-limited credential proving authorisation, renewed automatically in the background.
This is a genuine security improvement. It also introduces a state that didn’t previously exist: a credential that’s present but no longer valid. Under the old system your password either worked or it didn’t. Now the app can hold something that looks like a valid sign-in, fail with it, and ask for a password it doesn’t strictly even use in the old sense.
The common triggers are worth recognising:
- A password changed somewhere else. Change it via a browser or on a phone, and any device still holding the old credential starts failing.
- Multi-factor authentication being switched on. Very common for business accounts, and a device set up beforehand needs to complete the new sign-in flow.
- A security policy applied to the account, particularly on business tenancies, which can invalidate existing sessions across the board.
- A stale credential that simply failed to renew, sometimes after a machine has been off for a long period.
The practical advice is short. If Outlook is asking for your password repeatedly and you’re certain the password is right, stop entering it — you aren’t going to type your way out, and repeated failed attempts can occasionally trigger account protections and make things worse. The stored credential needs clearing and the account needs signing in afresh. If you’d rather not go digging in Windows’ credential store, that’s exactly the sort of half-hour job worth handing over.
Local Help in Putney SW15
If your email has stopped syncing, or you’re stuck in a password prompt that won’t take no for an answer, it’s usually an authentication problem with a quick fix — not a lost mailbox and not a broken computer.
Our workshop is on Lower Richmond Road in Putney, and for email problems we can often help remotely as well as in person. Call 020 7610 0500 or arrange email setup in Putney — it’s useful to know whether anything changed recently, such as a password reset or a new security step at work.
