Send a fax from Outlook by emailing your message to a fax-to-email gateway

Outlook can send a fax without a fax machine or dedicated fax service. You compose an email in Outlook, address it to a fax number converted into an email address, and the gateway service converts that email into a fax and delivers it to the recipient's fax machine. The fax arrives on the other end looking like a standard fax — the recipient sees it come through their fax machine, not their email inbox.

The process works because fax-to-email gateways act as intermediaries. They receive your email from Outlook, extract the content and any attachments, convert them to fax format, and dial the destination fax number. You do not need to install software or change how you use Outlook — you just address the email differently.

Key Takeaways

  • Fax-to-email gateways convert your Outlook email into a fax by translating the recipient's fax number into an email address format.
  • Common gateways include services run by your internet provider, Microsoft 365 fax add-ins, or standalone fax services like eFax or Fax.com.
  • You attach documents to your Outlook email as you normally would — the gateway handles converting them to fax-compatible formats.
  • Delivery usually takes a few minutes, and many gateways send you a confirmation email when the fax reaches the destination machine.

Find out which fax gateway your email provider offers

Your internet service provider or email host may already include fax-to-email as part of your account. Check your provider's website or call their support line to ask whether fax-to-email is included and what the email address format is. If you use Outlook through Microsoft 365 (the subscription version), Microsoft offers fax add-ins that integrate directly into Outlook — search "Microsoft 365 fax" in the Microsoft AppSource store within Outlook to see what is available in your region.

If your provider does not offer fax-to-email, you can sign up for a standalone service. eFax, Fax.com, and similar services let you send faxes through email for a monthly fee or per-fax charge. These services give you an email address or a specific format to use when addressing faxes from Outlook. Some offer free trials so you can test the service before committing.

Compose your email and address it to the fax number

Open a new email in Outlook. In the To field, enter the fax number in the format your gateway specifies. Most gateways use a format like 1-555-123-4567@fax.provider.com or 5551234567@efax.com — the exact format depends on which service you use. Check your gateway's documentation or support page for the correct format before sending.

Write your message in the email body as you normally would. The gateway will convert this text into fax format, so keep it clear and straightforward. Add a subject line if you want — some gateways include it on the fax cover page, though others do not.

Attach documents and check file compatibility

Attach the documents you want to fax by clicking Attach File in Outlook. Most gateways accept PDF, Word documents (.docx), images (.jpg, .png), and text files. Fax machines display everything in black and white, so color documents will be converted to grayscale. If you are sending a document that relies on color to be understood, convert it to PDF first so the gateway handles it consistently.

Keep file sizes reasonable — most gateways have limits between 5 and 25 megabytes per fax. If you are sending multiple large documents, split them into separate emails rather than attaching everything to one message. Check your gateway's size limits before sending.

Send the email and wait for confirmation

Click Send in Outlook. The email goes to your gateway's server, which then converts it and dials the fax number. This usually takes between one and five minutes. Many gateways send you a confirmation email once the fax has been delivered to the destination machine — check your inbox or spam folder for this confirmation.

If the fax does not go through, the gateway typically sends you a failure notice explaining why — for example, the number was busy, the fax machine was offline, or the file was too large. You can then resend the fax or troubleshoot the issue with the recipient.

Understand what the recipient sees

The person receiving the fax sees it come out of their fax machine, not arrive in their email. The fax includes any cover page your gateway generates (usually with your name and the date), followed by your message and any documents you attached. If you included a subject line, it may appear on the cover page depending on the gateway.

The recipient cannot reply to the fax through email — if they want to respond, they use their fax machine to send a fax back to your number, or they contact you by phone or email separately. Make sure your contact information is clear in the fax so they know how to reach you.

Troubleshoot common problems

If your fax does not go through, check that you used the correct email address format for your gateway. A single character wrong in the address will cause the fax to fail. Verify the fax number itself is correct — if the number is disconnected or the fax machine is turned off, the gateway will report a delivery failure.

If documents are not appearing on the fax, the gateway may not support the file format you used. Try converting the document to PDF and resending. If the fax is arriving but looks garbled or incomplete, the file may be too large or the gateway may have had trouble converting it — try a smaller file or contact the gateway's support team.

Frequently Asked Questions

Can I send a fax to multiple numbers at once from Outlook?

Most gateways let you add multiple fax numbers in the To field, separated by commas or semicolons depending on the service. Check your gateway's documentation for the exact format. The gateway will send the same fax to each number.

What happens if the fax machine is busy or offline?

The gateway will attempt to redial the number several times over a period of hours or days, depending on the service. If it cannot reach the machine after multiple attempts, you will receive a failure notification. You can then resend the fax or contact the recipient to confirm their fax machine is working.

Do I need a fax machine or phone line to send a fax through Outlook?

No. The gateway handles all the dialing and fax transmission — you only need your Outlook email account and an internet connection. The gateway uses its own phone lines to dial the destination fax machine.

Can I send a fax if I do not have a fax number to receive replies?

Yes, but the recipient will not be able to fax you back. Include your email address or phone number in the fax so they can contact you by another method if they need to respond.

Is there a cost to send faxes through Outlook?

It depends on your gateway. Some internet providers include fax-to-email at no extra charge. Microsoft 365 fax add-ins vary by region and plan. Standalone services typically charge a monthly subscription or a per-fax fee. Check your specific gateway's pricing before sending.