Short answer: an incoming fax that never arrives triggers no alarm — and that's exactly the problem. To avoid losing anything, you need three things: a second receiving number with a different provider, a shared mailbox rather than a personal one, and silence detection ("no fax received for 48 hours on a number that usually gets five a day"). Everything else — a written procedure, escalation contacts, a six-monthly test — fits on a single sheet of A4 and prevents 90% of serious incidents.
A sending failure is immediately visible: the transmission report comes back as failed, the user complains, you call support. A reception failure, on the other hand, is silent. For three days, a laboratory didn't receive test results from a partner, a law firm didn't receive a court summons, a town hall didn't receive a bid submitted by a candidate before the deadline. Nobody noticed anything, because nobody was specifically waiting for that particular document.
Here's how to organise reception so that silence becomes detectable.
What can break fax reception
There isn't one single point of failure, there's an entire chain of them. Each link has its own failure modes.
The incoming line. With the gradual shutdown of the copper network overseen by Arcep — whose timetable was in fact reworked by Orange in early 2026 for several million lines — fax numbers are migrating en masse to IP access. A fibre cut at building level, a power failure on the router, a router rebooted by an overnight update: on a fax machine connected to an analogue adapter, the line becomes unreachable and the sender gets a busy tone or no answer at all.
The online fax provider. Platforms go down too. An incident on a T.38 gateway, poorly announced maintenance, a saturated number pool: during the incident, inbound calls are rejected. Most services store received faxes and redeliver them afterwards, but not all of them, and not indefinitely.
Email delivery. This is the link most often to blame, and the most neglected. The fax did reach the platform, but the notification email never reaches the recipient: full mailbox, an overly aggressive filtering rule, a 9 MB PDF blocked by the antivirus gateway, a sender flagged as junk after an SPF record change, the address of an employee who left eight months ago.
The human factor. The fax lands in Nathalie's mailbox. Nathalie is on holiday. End of story.
Principle 1: never let reception depend on a named individual's mailbox
This is the cheapest fix with the best return. An organisation's fax number should deliver into a shared mailbox (fax@, reception-fax@, registry-fax@) monitored by at least two people, with a rule that automatically archives messages in a dedicated folder.
Three immediate benefits:
- one colleague's absence no longer creates a black hole;
- an employee leaving doesn't break the delivery chain;
- the history stays accessible to the organisation, not to an individual.
Add a second delivery address in copy, hosted somewhere other than your main email system. If your domain goes down, or if your filtering gateway starts discarding attachments, the backup copy remains readable. Many fax-to-email services accept two, three, sometimes five recipients per number: it's free, so use it. Our fax-to-email guide covers the settings on the receiving side in detail.
Principle 2: two numbers, two technical paths
Redundancy is only worth something if it takes a different route. Two numbers with the same provider, on the same gateway, in the same data centre, will go down together.
What real redundancy looks like:
| Configuration | Survives… | Doesn't survive… |
|---|---|---|
| One number, one provider | nothing | provider outage, access cut, email incident |
| Two numbers, same provider | loss of one local access line | a global provider outage |
| Two numbers, two providers | one provider failing, a local cut | an internal routing error |
| Primary online number + backup analogue fax machine | cloud outage, internet cut | the end of the PSTN at that site |
The most robust setup for a small organisation: a primary fax-to-email number, a secondary number with a second provider, both delivered into the same shared mailbox. Actual cost: a few euros a month. Benefit: one vendor's outage no longer brings you to a halt.
Be careful, though, not to create a communication trap. If nobody knows your backup number, it's useless on the day it matters. Two options: publish both numbers on your documents ("Fax: 01 XX / backup: 01 YY"), or keep the second one quiet but ready to be circulated by email and phone to your twenty main correspondents. That list of twenty contacts, kept up to date, is part of the plan — it's worth more than any piece of hardware.
Principle 3: detect the silence
This is the central idea of this guide, and it's rarely put into practice.
A professional fax number has a rhythm. A medical secretariat receives between three and fifteen faxes per working day; a law firm, two to eight. If the counter drops to zero for two working days, it's almost never a coincidence: it's a fault.
Set up a check, however low-tech:
- Weekly tally of the volume received. Most online fax interfaces display a log. Note the number of pages received each week in a simple table.
- Alert threshold. If the weekly volume falls below half the average of the last eight weeks, investigate.
- Monthly self-reception test. From another number, send yourself a test page. It's the only proof that a full chain works end to end. Two minutes a month.
- Check the junk folder. Once a week, someone opens the spam folder of the shared mailbox. That's invariably where the most urgent faxes end up.
Record these tallies in a spiral-bound logbook kept next to the relevant workstation, or in a shared spreadsheet: what matters is that the record exists and is time-stamped, because that's what will let you tell a correspondent "your fax of the 14th never reached us, here's our log".
Principle 4: keep a degraded path, not a phantom one
The fallback plan must be workable under the conditions of the outage. Two classic mistakes.
The backup fax machine unplugged since 2019. It's in the cupboard, it may even still have a cartridge, but the analogue line that fed it was cancelled. On a site still served by copper, a backup multifunction laser fax machine makes sense; on a site already migrated to fibre, it will only work through an ATA adapter properly configured for T.38 or G.711 — something you need to test, as we explain in our article on T.38 failures.
The backup access that relies on the same cable. If your plan B is to use the provider's web interface from the same office, a fibre cut wipes out plan B. A backup 4G/5G router, powered by a desktop UPS, turns a three-day outage into a ten-minute interruption. It's the same equipment that saves a video call or a point-of-sale terminal; the investment is justified well beyond fax.
Think about power, too. A fax machine, a router and an ATA all on the same power strip, and the neighbourhood's first micro-outage leaves your reception dead until the next morning, when someone remembers to switch everything back on in the right order.
The continuity sheet: one page, not thirty
A full business continuity plan, in the sense of the ISO 22301 standard, goes far beyond the subject of fax. But for fax reception, a one-page sheet is enough — and it will actually be read, unlike the 80-page binder.
What it contains:
- The numbers involved and which department each belongs to.
- Provider, contract reference, support phone number and opening hours.
- Delivery addresses (primary, copy, backup) and who has access to them.
- Switchover procedure: who decides, who informs whom, what template message to send to correspondents.
- List of the twenty priority correspondents with phone and email.
- Incident log: date, duration, cause, fix.
Print it out. Yes, on paper — the day the network goes down is precisely when you'll need it, and a lever arch file with punched pockets sitting at the front desk holds up better than a file stored on an unreachable intranet. Keep one copy at reception and one with the person on call.
Special cases: healthcare, law, public procurement
Healthcare. Lab results, imaging reports and discharge letters still travel largely by fax, even though secure health messaging systems (MSSanté) are gaining ground. A reception failure has a direct clinical impact. The plan must therefore include an explicit alternative channel, communicated to regular correspondents, and the receiving mailbox must remain compliant with health data confidentiality requirements: encryption, traced named access, no forwarding to personal addresses. Our fax and GDPR feature covers this aspect.
Legal professions. Procedural deadlines don't stop because your gateway is down. Keep proof of the outage: screenshots of the provider's status page, emails from support, a reception log showing the gap. That's the only material you'll have to justify an incident to a colleague or a court.
Public procurement. When a notice still allows submission by fax, a reception failure on the buyer's side creates litigation risk. As a bidder, never leave it to the last hour: send, check the report, and duplicate via the channel set out in the tender rules.
Test twice a year, for real
An untested plan is a hypothesis. The exercise takes thirty minutes, twice a year:
- Simulate the failure of the primary number (disable it, or unplug the ATA).
- Ask a willing correspondent to send a fax to the backup number.
- Check that it arrives in the shared mailbox, legible and complete.
- Time the gap between the start of the incident and the effective switchover.
- Note what went wrong — something always does — and update the sheet.
Many organisations discover at this point that their backup number hadn't been paid for, that the shared mailbox no longer existed after an email migration, or that the only PDF received was 40 KB for six illegible pages because the resolution had been left on draft mode. Better to find out on a quiet Tuesday than on a Friday deadline.
Frequently asked questions
Is a fax sent during an outage permanently lost?
Not necessarily. Under T.30, a sender that gets no answer generally retries several times depending on its settings, and most online fax services queue incoming faxes for redelivery. That said, if the call was rejected with a busy signal, the sender may have given up after three attempts, without you keeping the slightest trace of it.
How much does a real fax continuity plan cost?
A second number with another provider costs a few euros a month. The rest is time: an hour to write the sheet, ten minutes a month for tests, half an hour every six months for the exercise. It's the cheapest continuity arrangement an organisation can put in place.
Should you keep a physical fax machine "just in case"?
Only if the site still has a usable line or a tested ATA, and if someone checks the device from time to time. A silent fax machine in a cupboard isn't a fallback plan, it's an object. Also check that consumables are still available: some older models no longer have a compatible toner cartridge on the market.
How do I notify my correspondents during an incident?
Prepare the template message in advance, before you need it: two sentences stating that the usual number is temporarily unavailable, the replacement number, and a fallback email address. Send it to your list of twenty priority contacts. Without a ready-made template, this communication takes two hours instead of five minutes.
Does moving to VoIP make the risk worse?
It shifts it. The copper line was resilient to software failures but physically fragile and doomed; IP is more flexible but depends on electricity, the network and a codec negotiation that can be temperamental. The real answer is neither one nor the other: it's redundancy, and gradually phasing out fax wherever a compliant digital channel already exists.
Key takeaways
- A reception failure is silent: without a volume indicator, you won't see it.
- Always deliver to a shared mailbox, never to a single named address.
- Two numbers with two different providers are worth more than ten with one.
- Plan an independent backup route (4G, UPS) and test it.
- A printed, up-to-date one-page sheet, with the list of priority correspondents.
- A monthly self-reception test and a six-monthly exercise: thirty minutes that save case files.
- Check coverage for your overseas correspondents on the supported countries page before giving them a backup number.
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