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SFLetter.com: overview of the service

SFLetter.com is a free service to protect documents to be sent via email. The objectives of the service:

  • To keep an email message as well as the contents of attached documents secret– the recipient will not be able to forward or copy the protected files.
  • To track when a protected email is opened by the addressee and to track attempts of unauthorized access to protected files.

Who can benefit from using SFLetter.com?

  • Company employees who need to send sensitive information to inform partners or clients promptly with the possibility to track when emails are opened.
  • Internet publishers who send news to subscribers on a chargeable basis.
  • Individuals that send information of a personal nature for distribution in their "narrow circle": an essay for a friend to read or "crazy" photos from a party.
  • Freelancers and companies who are involved in creative or analytical activities.

How it works

SFLetter.com is a secure email service. To use it, you first need to sign up for a mailbox. Then the sender composes an email, adds files, selects the appropriate variant of protection (to protect attachments, the message or both) and clicks the "Send" button.

The addressee receives a protected email as a usual email. He or she doesn’t need to register an account at SFLetter.com. The protected files are downloaded to a device with either Windows, Android, iOS and macOS. The recipient also downloads and installs StarForce Reader, a program to open protected files. It works much the same as Adobe Reader, but besides PDF documents it can also open protected files.

The fact that the files were opened is logged in the report available to the sender.

Afterwards, protected documents can only be accessed on the device where they were opened for the first time. This is because the files were "locked" to a particular hardware configuration of a computer or a phone during activation. The second component of protection is a check of the actual access permissions. The sender can revoke the right to view the document at any time (Premium account feature), so this check is carried out at regular intervals.

Sending protected bulk emails

With SFLetter.com you can send protected bulk emails directly from your mailbox. This is very convenient if there is a need to send protected emails on a paid subscription to a group of recipients; and for corporate purposes to send email messages with confidential information to a certain circle of persons.

Also you can integrate your SFLetter.com mailbox with third-party bulk email services using SMTP settings. Read more.

Features of Premium and Business accounts

SFLetter.com offers Premium and Business accounts to get access to extended features of the service:

  • Access revocation for sent emails.
  • Time limited access to protected files.
  • Offline access management.
  • Enlarged mailbox size.
  • Use of a client’s domain name instead of SFLetter.com for outgoing mail.

Common information about SFLetter.com

User interface languages: English and Russian. Other languages can be made available upon request.

Mailbox registration: for free.

Launch date: July 2014.

Protection methods: code obfuscation, binding to a user device, digital right management (DRM), container technology. Encryption technologies are not used.


What is the difference between the protection technologies used by SFLetter.com and mail services with encryption?

Encryption can’t provide full protection for emails and attachments: after decryption the recipient can do whatever he/she wants with the protected files. SFLetter.com protects documents against fraudulent actions of addressees. Thanks to technology that binds documents to one specific user device, it is impossible to open messages and attachments on any other devices. This makes it pointless to forward a protected email to third parties.

What sense does it make to use SFLetter.com if you can take a photo with your phone camera?

The solution does not prevent opened documents from being photographed with a camera (there is protection against screen grabbing software though!). But this practice has a number of issues:

  1. The recipient taking the photo understands his action is unauthorized because he was informed in advance about the status of the documents.
  2. The sender can track the time the documents were opened and the IP address where the leakage occurred.
  3. Pictures may not have the quality of the original document.

Is it safe to install StarForce Reader, the viewer program, on my phone and computer?

We often download and install software for different purposes. To open files with extensions SFPDF and PCDOC you need StarForce Reader. This software is developed by Protection Technology and signed with its signature. And it is absolutely safe for user devices if you download it from those two official websites: SFLetter.com or SFContent.com.

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