A device using an old password can get your office's internet address blocked by the host's firewall. Give the host that address, find the device named in its log, update it, then have the block lifted.

Down at the office, fine everywhere else

Monday morning, nobody in the office can open the company website. Email stops arriving, Outlook cannot connect, and webmail just spins.

The host's support line says the server is fine. A phone on mobile data, off the office Wi-Fi, loads the site and collects the mail.

The server is up. It has decided your office is attacking it, and it is refusing every connection from your address.

The cause is usually small and inside the office: a phone, a tablet or a copier still trying an email password that has changed.

Why one device blocks everyone

Every computer, phone and printer in an office reaches the internet through one router. To the outside world, they all share its single public address.

Servers face automated password guessing all day, against email, FTP and website logins. So most hosts run security software that counts failed sign-ins from each address.

Past a set number in a short time, the firewall blocks that address. Not just for email: for the website, webmail, FTP and everything else on that server.

A device repeating a wrong password every few minutes looks exactly like a guessing program, and the block falls on everyone behind your router.

Where an old password keeps trying

The fourth is the one nobody thinks of. A copier that emails scans signs in with a stored password, and its errors appear on a small screen nobody reads.

How it usually starts

Most blocks follow a password change. Someone leaves, a password is suspected, or the host asks for a stronger one.

The person making the change updates their own devices; the forgotten ones keep trying the old password. A mail app checks every few minutes, day and night, so a weekend easily reaches the limit.

Getting the block lifted

You need your office's public address. From an office computer, search Google for what is my IP, and it appears at the top of the results.

Phone the host, or write from a personal email account, since your own mail may be unreachable. Give them the address and ask for the block to be lifted and for the login that was failing.

The firewall's log usually names the account and the service, such as the shared mailbox signing in to collect mail. That narrows the search to the devices using that account.

Some blocks lift by themselves after an hour or so. Repeated ones can become permanent until the host removes them.

A worked example

A permit expediter with four staff prepares and tracks building permit applications for homeowners, builders and restaurant owners, from a second-floor office above a row of shops.

On a Friday afternoon the owner changed the password on the shared office mailbox after an assistant left. He updated his own phone and the two office computers, and went home.

On Monday nobody in the office could open the website or send email. The host found hundreds of failed sign-ins on the shared mailbox from the office's address, and a block that had begun on Saturday night.

The source was a tablet in the meeting room, used to show clients their drawings, which had checked the mailbox every fifteen minutes all weekend.

The owner found a second device on the old password while looking: the copier, which scanned drawings to the shared mailbox and would have failed with the morning's first scan.

Both were updated, the host lifted the block, and the office was working before eleven. The copier now has its own line on the list of everything using that mailbox.

Find the device before asking again

Lifting the block before the device is fixed only resets the count. The same tablet will have the office blocked again by lunchtime.

Start with the account the log names, then check everything that might hold it: phones, tablets, laptops, the copier and any software that sends email.

If the culprit stays hidden, change the office Wi-Fi password so unknown devices drop off, then reconnect the ones you recognise.

Remove the mailbox entirely from devices that no longer need it. A device without the account cannot keep trying it.

Changing a password without locking yourself out

Before the next change, write down every device and program that uses the mailbox, including the copier and the accounting software.

Choose a quiet time for the change, and update each item on the list straight away rather than over the following days.

The next morning, check from the office that the website and email both open. A block caught then costs ten minutes, not a lost Monday.

Should the office be on an allow list?

Many hosts can put an address on an allow list, so the firewall never blocks it.

It only works if your internet provider gives the office a fixed address. Many business connections change address from time to time, and an entry for an old address does nothing.

It also switches off a protection. An allowed address can fail to sign in as often as it likes, which matters if a computer in the office is ever infected.

Some hosts refuse on shared servers, so ask what yours recommends.

The counter-case

The firewall is doing its job. The rule that blocked your office also stops a constant stream of guessing, and switching it off would trade a rare nuisance for a real risk.

Where email is handled by Office 365, Google Apps for Work or another separate service, an old email password will not take the website down, though those services have lockouts of their own.

Blocks are rare for a one-person business with one phone. For an office with several devices on one connection, list every device that uses a password before changing it.

Before the next password change

  1. List every device and program using the mailbox.
  2. Include the copier and the accounting software.
  3. Remove the mailbox from devices nobody uses.
  4. Change the password at a quiet time.
  5. Update every listed device within the hour.
  6. Check the site and email from the office next morning.
  7. Keep the host's phone number somewhere besides email.

Step one does most of the work. Every block like this comes from a forgotten device, and a written list is the reliable way to remember them all.

Another way the host's security software can surprise a business is covered in when the host's scanner removes a file.

Frequently asked questions

Why can only the office not reach our site?

The host's firewall has probably blocked your office's internet address after repeated failed sign-ins from a device there. Phones on mobile data and staff at home are unaffected.

What causes the failed sign-ins?

Usually a phone, tablet, copier or program still using an old email password after a change. It retries every few minutes, which looks like someone guessing passwords.

How do we get the block lifted?

Find your office's public address, then phone the host or write from a personal account. Ask them to lift the block and to say which login was failing.

Why does the block keep coming back?

Because the device is still trying the old password. Lifting the block only resets the count, so find and update the device before asking again.

Should our address go on an allow list?

Only if the office has a fixed address from its internet provider, and accepting that the address then escapes the firewall's protection. Ask your host first.

How do we avoid this next time?

Before changing a password, list every device and program that uses it, including the copier. Update them all at once, then check from the office next morning.

West Coast Media Solutions Inc. provides web design, web development, hosting, digital marketing, and business consulting to organisations across Canada, drawing on more than twenty-five years in the field.

Website and email gone at the office only?

Call us with your office's internet address. We will work with your host to find the device and lift the block.

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