LetterAgent
Mail physical letters by just asking your AI assistant.
Home > Guides > Why did my fax fail
A fax usually fails for one of a few reasons: a busy line, a wrong or disconnected number, line noise that breaks the connection, or a problem at the receiving machine. Check the number first, then the error message, and confirm with the recipient before simply resending the same document.
A busy signal is the simplest failure and the easiest to fix: the receiving machine was already on a call, or its line was in use. Wait and try again, and if the line stays busy across several attempts at different times of day, call the recipient on a voice line and ask whether their fax number is still correct and whether the machine is working. A number that is busy every time you call, at every hour, may have been reassigned to voice use, or the machine may be switched off.
A "no answer" failure is different. It means the call rang out without a fax machine picking up. That happens when the number belongs to a voice phone, when the fax machine is set to manual answer and no one pressed receive, or when the machine is out of paper or switched off. A "no answer" result that repeats is a reason to call the recipient, not to keep redialing. Repeated blind retries can tie up your own line and, with some services, send partial pages that confuse the recipient.
| Error or sign | Likely cause | First step |
|---|---|---|
| Busy signal | Receiving line in use | Retry later, then call to confirm the number |
| No answer | Voice line, machine off, or manual answer | Call the recipient and ask them to check the machine |
| Poor line condition | Noise or a weak connection drops the call | Retry, and try a slower speed setting if your service offers one |
| Communication error mid-send | Connection broke partway through | Confirm which pages arrived before resending |
| Wrong number reached | Dialing error or outdated number | Verify the number from a second source before resending |
Yes, more often than people expect. A document with very dark pages, dense photographs, or fine reversed text (white letters on black) takes far longer to transmit and is more likely to hit a timeout or a line error. Pages that are blank, or nearly blank, can also confuse some machines, which may treat them as errors. If a fax fails repeatedly at the same page, that page is the suspect: re-scan it at a normal contrast setting, remove heavy shading, and try again.
Very long faxes fail more often than short ones, simply because a longer call has more chances to be interrupted. If a long document keeps failing, split it into smaller batches and confirm each batch arrived. That also limits the damage if one batch fails: you resend a few pages, not the whole file.
Fax was built for old copper phone lines, and it is sensitive to noise and delay that voice calls tolerate without complaint. Static, echo, or packet delays can break the fax handshake, the opening exchange in which the two machines agree on speed and format, or drop the call mid-page. Internet-based phone lines are a frequent source of this trouble: the voice compression that makes internet calls sound fine can scramble fax tones. If your fax service runs over an internet phone line and failures are common, suspect that line first.
Error correction mode, a feature on most fax machines and services, helps here. It checks each block of data as it arrives and asks for a repeat of any block that arrived corrupted. Turning it on slows the fax slightly but makes success far more likely on a noisy line.
Often. A receiving machine out of paper, out of toner, with a full memory, or with a paper jam will reject incoming faxes, and the error message on your end may not explain why. You cannot fix any of this from your end, which is why a quick voice call to the recipient solves more fax failures than any setting change. Ask them to check paper, toner, and jams, and to confirm the machine is set to receive automatically.
Also check the time. Some offices switch their fax machines off at night or set them to manual answer outside business hours. A fax that fails at midnight may succeed in the morning with no other change.
Resending blindly is the one move that makes things worse. It can deliver duplicate pages, create confusion about which version is current, and, if the original failure was a wrong number, send your document to a stranger a second time. A two-minute check with the recipient prevents all three.
LetterAgent fax is currently available in testing, so it is described that way here, not promised for any specific send. When you send a fax through LetterAgent, you ask your AI assistant, approve the exact quoted total after the page count is verified, and pay once through Stripe. If a fax fails, the same checks apply: confirm the number, confirm with the recipient, and ask your assistant about the job's status before resending. LetterAgent fax numbers cover the United States and Canada only, and there is no inbound fax, so a recipient cannot fax you back through the service.
Ready to fax it? Fax with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is sent.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
Need help? Ask your assistant: it can check a job's status any time. If it ever can't handle something: hello@getletteragent.com