Email-to-fax works by converting your message into a fax and routing it through a gateway service

To send a fax from your email, you address a message to a special email address that includes the recipient's fax number, then send it as you normally would. The gateway service receives your email, converts it to fax format, and dials the fax number on the other end. The recipient sees a standard fax arrive at their machine — they do not receive an email and do not need any special software.

The process takes the same time as a regular fax, usually a few seconds to a few minutes depending on document length and the recipient's fax machine. You do not need to own a fax machine or subscribe to a fax service. The main limitation is that the recipient's fax number must be working and answered by an active fax machine.

Key Takeaways

  • You send an email to an address formatted as the fax number plus a gateway domain, such as 5551234567@efax.com or 5551234567@fax.com.
  • The email subject line becomes the fax cover page, and attachments (PDF, Word, image files) become the fax pages — do not include body text you want the recipient to see.
  • Some gateways are free for a limited number of faxes per month; others charge per fax or require a monthly subscription.
  • The recipient receives a standard fax on their fax machine with no indication it came from email unless you note that in the cover page subject line.
  • Fax delivery can fail silently if the number is wrong, the machine is offline, or the line is busy — many gateways send you a delivery confirmation email.

Choose a gateway service and learn its address format

Common free or low-cost gateways include eFax, Fax.com, HelloFax, and Google's built-in fax feature (if you use Google Workspace). Each has a different email address format. eFax uses the format phonenumber@efax.com. Fax.com uses phonenumber@fax.com. Some services require you to register first and assign a personal fax number; others let you send to any number without an account.

If you use Gmail through Google Workspace (the paid business version), you can send a fax directly from Gmail without a separate gateway — look for the "Fax" option in the compose window. If you use personal Gmail, you will need to use a third-party gateway. Check the gateway's website for the exact format it expects, because some require country codes or specific spacing.

Prepare your document and address the email correctly

Save the document you want to fax as a PDF, image file (JPG or PNG), or Word document. Attach it to a new email. In the "To" field, type the recipient's fax number followed by the gateway's domain — for example, 5551234567@efax.com. Do not include dashes or parentheses in the fax number unless the gateway instructions specifically say to.

The email subject line will print as the fax cover page, so write something clear like "Fax from [Your Name]" or "Invoice for [Date]". Do not put important information in the email body — most gateways ignore body text and only send what is in the subject line and attachments. If you need a formal cover page with your company details, check whether the gateway lets you upload a template.

Send the email and watch for delivery confirmation

Click Send. The gateway receives your email, converts the attachment to fax format, and dials the recipient's fax number. This usually happens within seconds, though busy lines or slow machines may add a minute or two. You will receive a confirmation email from the gateway when the fax is sent — read it carefully, because it tells you whether delivery succeeded or failed.

If the confirmation says "failed" or "no answer," the fax number may be wrong, the machine may be offline, or the line may have been busy. Try sending again, or call the recipient to confirm the number is correct and the fax machine is on. Some gateways let you schedule a retry automatically.

Understand what the recipient sees on their end

The fax arrives at the recipient's fax machine as a standard fax. The cover page shows your subject line at the top, followed by the pages from your attachment. The recipient does not see an email address or know the fax came from email unless you write that in the subject line. If your gateway assigns you a fax number, that number may appear on the recipient's fax machine display or cover page, depending on the gateway and the receiving machine.

The recipient can print, file, or discard the fax like any other fax. They do not need to do anything special to receive it, and they cannot reply by email — if they want to respond, they must fax or call you back.

Know the limits and costs of different gateways

Free gateways usually allow 5 to 10 faxes per month at no cost, then charge per fax after that. Paid services range from $5 to $20 per month for unlimited faxes, or 25 cents to $1 per fax on a pay-as-you-go plan. Some gateways charge more for international faxes. Check the gateway's pricing page before you send, especially if you plan to fax regularly.

Free gateways may add a watermark or banner to your fax, or may take longer to deliver. Paid services usually deliver faster and without marks. If you fax only occasionally, a free gateway is usually enough. If you fax more than a few times per week, a monthly subscription often costs less than pay-per-fax rates.

Troubleshoot common problems

If your fax does not go through, first check that the phone number is correct and formatted without dashes or parentheses. Confirm the recipient's fax machine is on and has paper. Try sending again — a busy line or temporary machine error can cause a single failure. If it fails twice, call the recipient to verify the number.

If the fax arrives but looks blurry or cut off, the problem is usually the document format or size. Try converting the file to PDF if it is not already, or reduce the file size by lowering the image resolution. Some gateways have a maximum file size (often 10 to 25 MB); if your document is larger, split it into multiple faxes.

If you never receive a delivery confirmation email, check your spam folder — confirmation emails sometimes get filtered. If it is not there, log into your gateway account and check the sent fax history. Most gateways keep a record of every fax you send for at least 30 days.

Frequently Asked Questions

Can I send a fax to an international number?

Yes, but most gateways charge more for international faxes — often $1 to $3 per fax instead of the domestic rate. Include the country code at the start of the number (for example, 441234567890 for a UK number). Check the gateway's pricing page to see which countries it supports and what the cost is.

What file types can I send as a fax?

Most gateways accept PDF, JPG, PNG, GIF, TIFF, and Microsoft Word or Excel files. PDF is the safest choice because it preserves formatting. Avoid sending text files (.txt) or web pages — they may not convert to fax format properly. If you have a scanned document, save it as a PDF or image file.

Can I send a fax without an attachment?

No. The gateway needs an attachment to convert to fax format. If you want to send only a cover page with a message, create a straightforward one-page document (Word, PDF, or image) with your message and attach that. The subject line alone will not be enough.

Does the recipient know the fax came from email?

Not unless you tell them in the subject line or cover page. The fax looks like a standard fax from a fax machine. If your gateway assigns you a fax number, that number may show on the recipient's display, but they will not see an email address or know it came from email.

What happens if the fax number is busy or the machine is offline?

The gateway will try to send the fax, fail, and send you a delivery failure notification. Some gateways automatically retry a few times over the next hour or two. If it keeps failing, call the recipient to confirm the number is correct and the machine is on, then send again.