Knowledge Base - FlexFax: User Manual - Sending By Email (Complete Reference)

Detailed Reference

This guide reviews more details on each of the options and other information like supported attachment formats, for a quick reference on sending your first fax please see this document.

Authorized Users

Access is restricted by the combination of email address and the fax number you are sending as. If you want a new person to be able to send, their email address needs to be listed. Emails received from unlisted email addresses will not be acknowledged or responded to. To add people to your list of Authorized Users, simply contact Client Support with the email address, fax number, and customized Caller Name is desired.


Supported Attachment Formats

We are able to support many different types of images. Over time additional formats may be added. Please keep in mind that software vendors are often enhancing options available in their applications - this makes support of some formats (notably office documents) harder than some other formats. If you need to be sure of the layout confirm or specify details layout options, please consider saving the desired portions as PDF prior to sending.

Extension Description
TIFF / PDF TIFF (Tagged Image File Format) and PDF (Portable Document Format) are both excellent formats to use for faxes. Both formats support multiple pages within a single document and can combine images and text in a scalable format (or can be used for scans). The standards are well established. If you have trouble with any other format, try converting your file to TIFF or PDF prior to sending.
HTML HTML is not supported as an attachment but is supported for cover pages from within the email body. When images are included inline in the cover page, they are scaled to fit where appropriate as the page is rendered for a letter or legal-size paper.
GIF / JPG / PNG Images are scaled to fit one image per page. If you include a cover page, which may include a signature with images, all the images are converted and included in their place on the page.
DOC / DOCX Word documents are sent much as they would print - they are assumed to print on 8.5" x 11" (letter) or 8.5" x 14" (legal). Using other paper sizes may have unexpected results.
PPT / PPTX Power Point presentations are faxed rotate to landscape orientation and printed one slide per page.
XLS / XLSX Excel spreadsheets can be complicated owing to the various ways page breaks can be specified, multiple tab formats, etc. All tabs in a spreadsheet will be sent - if you need to send a single tab you need to save a copy that tab to a separate spreadsheet prior to sending. 
TXT / CSV Text files or CSV files (which are text with commas between) are supported. Lines will be wrapped as required.


Limitations of Conversion

We strive to support a wide variety of document formats to make the process of sending faxes as easy as possible but there may be formats, we are unable to convert as you had intended. When that happens, we advise you to convert your document to a PDF and send using that PDF attachment using 8.5" x 11" (letter) or 8.5" x 14" (legal) paper size. PDF documents are already sized on standard paper formats and by viewing the PDF before sending you will have a very accurate idea of what the fax will appear as.

Documents most likely to suffer from conversion limitations would be XLS / XLSX files or anything where the document is configured to use a non-standard page size (something other than letter or legal sized paper).


Maximum Pages

The maximum pages that can be sent is limited to ensure your account is not accidentally abused. Attachments could contain hundreds of pages in spreadsheets or XLS / XLSX spreadsheets. If you send a fax that exceeds your maximum page limit, we will return a rejection along with the page count in the fax. Please contact Client Support to have your Maximum Page Limit raised. Please keep in mind this limit is in place to prevent accidental abuse of your account.


Maximum Faxes Per Hour

As a fraud / abuse control mechanism, we can detect and limit the number of individual faxes sent per hour (the default limit is 10 - or about one every 6 minutes on average). If you exceed that limit, your attempt to send will be rejected. Retry as per the note in the rejection message or contact Client Support to have your limit raised. Please keep in mind this limit is in place to prevent accidental abuse of your account.


Cover Pages [C or L]

Sometimes you may need to send a cover page with a document. FlexFax can make a cover page directly from your email body. Normal faxes sent will ignore the contents of the body - so any notes for your own purposes or default email signatures will be ignored and not sent.

The email body including signature and any images embedded will be formatted on one or more 8.5" x 11" (letter) pages and send as the cover page. It can be a great way to send a quick note by fax without going to the process of making a separate document.

When you need a cover page, add a "C" to the end of the subject line. If you need your cover page to be formatted for legal size paper, add an "L" to the end of the subject line.


Page Sizes

Both 8.5" x 11" (letter) and 8.5" x 14" (legal) page sizes are supported, however, a fax uses a single page size. If you send a letter size cover page ("C"), subsequent legal pages from attachments will be scaled to fit on letter size paper. There is an option to force a legal ("L") size cover page to allow for proper transmission of legal-size attachments. Keep in mind, that the receiving machine may print legal-size pages on legal paper or may be configured to scale them down and print them on letter size paper.


Standard vs. Fine Mode

Fax transmission mode is determined by the sender. There are two standard transmission modes.

  • Standard is 200 dpi x 100 dpi
  • Fine is 200 dpi x 200 dpi

When transmitting a document with small printing or detailed drawings, Fine Mode can improve the sharpness and detail of the fax sent. Fine Mode can improve the sharpness or detail and can improve a fax machine's ability to render an image.

Fine Mode will not improve the quality of a document that is too low in resolution to benefit from Fine Mode (such as a return fax of a document sent in Standard Mode) or a low-resolution picture, etc.

Fine Mode faxes can take much longer to send and do count towards your usage as 2 Standard Mode pages for each Fine Mode page sent.

When you need to send in Fine Mode, add a "F" to the end of the subject line on your email.


International Faxing

Sending faxes over international lines can be tricky and can be expensive - to protect our clients we configure faxing to work for non-premium NANP (North American Numbering Plan) destinations by default. Premium locations and countries outside the USA and Canada can be enabled by contacting Client Support.

International faxes must be sent exactly as they would be dialled. For more information on international dialing click here.



Journals (lists of faxes received and sent) can be prepared. There is a separate receive journal function which, if enabled, will be delivered to the same address as received faxes.

Each authorized user can have one of three types assigned. 

Type Description
Master Includes all faxes for the previous day including both sent and received for all users of that fax number. For received faxes, the journal can allow the recipient to resend the email if the email was misplaced, filtered, or mistakenly deleted. Includes a column to identify the sender.
Confirmation Includes all faxes sent by that user.
Errors Includes only faxes that did not send successfully.
None Generates no journal.



Fax transmission can be affected by noise on the line. Some fax machines may produce streaks or other artifacts of the scanning and compression process. This is considered normal, but in general by using electronic formats we minimize the effects you might see.

If you have trouble we can help. The system should provide an explanation of any error conditions but if anything doesn't seem to work as expected please let us know!


Contacting Support

When reporting an issue, we need to know as much information as possible to find the event in our logs. Please provide:

  • your fax number
  • the other fax number
  • the approximate date / time
  • the direction (sending or receiving)
  • the document id from the confirmation or journal
  • a description of the problem


Please let us know if you have any questions or think there's anything we can do to improve this guide!

Applies To

All Products

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