Email to fax is a service that turns your email into a fax. To send a fax from email, address the message to the recipient's fax number at the provider's fax domain. Your attachment becomes the fax pages. The provider dials the number and emails you the result. You need an account with an email-to-fax provider. A plain mailbox cannot send a fax alone, because a fax is a telephone call and a mail server does not place calls. The other routes are in how to send a fax.
The address
The address combines the full fax number with the provider's domain, like 15550000001@example-fax.net. Here, example-fax.net stands in for your provider's fax domain. Replace it with the exact domain listed in your account. Some providers require the country code with no plus sign. Follow the provider's rules for spaces and punctuation.
Put the fax address in the To field. Attach your document as a file. The subject or message body often becomes the cover sheet. Check the cover sheet rules before putting private information in either field.
Check the destination against the recipient's current fax number before you press Send. A correctly formatted address still reaches the wrong office if the number is wrong.
What the attachment must be
PDF is the safe choice because it keeps the page layout you checked. Images also work when the provider accepts their format. Office files depend on the service's converter. Export those files to PDF when you need to control page breaks.
The provider renders your attachment as black and white fax pages. Standard resolution is 204 by 98 dpi. Fine resolution is 204 by 196 dpi. Both come from ITU-T T.4, the standard for Group 3 fax terminals.
Small grey text can disappear. Colour distinctions do not survive conversion to black and white. Use dark text on a plain background. Give chart lines labels that remain useful without colour. Check for cropped edges and blank pages in the PDF before attaching it.
The return mail
A success email reports that the receiving fax machine confirmed the pages. This confirmation is part of the transmission procedure in ITU-T T.30. The signal is called MCF, message confirmation.
Check whether the email reports the final fax result or only acknowledges your request. A message in your Sent folder only records the email leaving your mailbox. It does not prove that a fax call finished.
A failure email can report a busy line or no answer. An invalid number can also stop the call. Follow the reported reason before trying again.
Keep the result email with the document you sent. It is your transmission record. A machine's page confirmation does not prove that a person read the document.
Where email to fax breaks
Your sending address must be registered with the provider. An unregistered address can cause the message to be rejected or dropped. Check the From field when your mail app has multiple accounts.
Forwarding a conversation can add signature logos and inline images to the fax. Start a fresh message. Attach only the document you want the recipient to receive. Remove quoted replies from the body if it becomes the cover sheet.
Some mail clients replace attachments with download links. The fax service then receives a link instead of a PDF. Unless the service explicitly supports fetching that link, there are no document pages to convert. Choose the option that attaches the actual file.
A received fax notification is also easy to mistake for ordinary correspondence. Replying to it does not email the person who faxed you. The notification comes from the service. To answer by fax, create a new send addressed to the other person's fax number.
Email to fax for software
A script can send mail to a fax address. Sending mail alone gives it no price quote or idempotency control. Resending the message can start another fax. Failure reports arrive as emails for a person to read unless you build a parser.
Fax for Agents is an API for software and agents. It does not provide an email-to-fax mailbox. Upload a PDF through its fax API. Request a quote for your destination. The quote fixes the send details and price for ten minutes. Submit it with an Idempotency-Key after human approval or under an administrator's delegated policy.
The API returns a job id in state queued. A job moves through active before an outcome is recorded. It becomes delivered only when the provider's confirmation of every page is stored. The job can also end as partial or failed. The unknown state means there is no outcome yet. It does not trigger automatic retransmission.
Signed webhooks report state changes to your application. Verify the signature before changing your own records.
Sending to the United States and Canada costs $0.039 per page, as of 2026-10-28. Cover sheets count as pages. Failed sends are not charged. For a partial result, only pages confirmed by the provider are charged.
Through the receive fax API, your application gets a signed fax.received event. The PDF has a private signed download URL that expires after ten minutes. Your program gets a defined event to handle without parsing a mailbox notification.