It’s Simple! This is How You Can Open .P7S Files

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How to Open .P7S Files

Just because the .p7s file doesn’t open in your system, it doesn’t mean it is unimportant. It could be containing valuable information. Therefore, instead of simply ignoring or deleting it, go through this Techspirited post and find out how you can open a .p7s file on your computer, phone, or other devices.


Renaming a file having a .p7s extension with some other extension will not result in automatic file conversion. Only by using a special conversion software can you change a .p7s file to another one

If there is one thing that the world of computers can boast of having, it is variety. There are literally thousands of different types, formats, and extensions for everything out there. So great is the magnitude of it all, that even your latest and most capable personal computer, having a multitude of software and application programs running on it, might sometimes end up finding something that it just doesn’t recognize, and hence fails to open.

Has the above scenario ever happened at your end? Was a file with a .p7s extension involved in it? If your answer is in the affirmative, then surely you have landed up on the right page. In the following lines, we will describe what a file having .p7s extension is, and how to open it in case you get one in your email.

What is a .P7S File?

Files that have the extension .p7s are email messages which are used by your computer’s email management program to send, receive, or simply view secure emails containing digital signatures. Microsoft Outlook 2010, PostBox, and Mozilla Thunderbird are a few of the programs that use the .p7s format extension.

These programs are capable of encrypting and decrypting email messages in the .p7s format, in order to secure them. Files with this extension also contain certain details, such as the source of origin of the email, date and time when it was sent, whether it has been modified during transmission, etc. The management applications with .p7s file support use this information to verify the legitimacy of the received email, to check whether it was received from a trusted source, and to ensure that it wasn’t tampered with.

If the user’s email management software doesn’t support a .p7s format, an email encrypted using this technology may be sent as an attachment, which is usually received as a smime.p7s. The software at the sending end integrates the Public-Key Cryptography Standard #7 or PKCS #7 technology, for digitally affixing encrypted signatures to the email.

How to Open a .P7S File Format

If you have received a file having a .p7s extension, you can open it using the following methods.

Step 1

The first step would be to make sure that you have the correct program needed to open a .p7s file, installed in your system. The following is a list of programs classified according to the different operating systems, that can be used to open .p7s files.

On Windows
1) Microsoft Outlook

Description: Microsoft Outlook is an information managing program offered by Microsoft as a part of the Microsoft Office suite. Especially designed for the Windows OS, this software program can be used as an email application, contact manager, notification manager, journal, and even for web browsing.

2) Mozilla Thunderbird

Description: Developed by the Mozilla Foundation, Mozilla Thunderbird is a free, cross-platform, open-source email, news and chat client. Among its variety of features include, online message management, junk and spam filtering, support for extensions and themes and security.

3) Postbox

Description: Postbox is a commercial email client developed by a start-up founded by Scott McGregor, who was formerly a lead engineer of the design team of Mozilla Thunderbird, and Sherman Dickman, who was formerly director of product management at Mozilla Corporation. It requires you to pay for any updates, and doesn’t have an open-source version for Linux.

1) Apple Mail

Description: Apple Mail, also known as or simply Mail, is an email program that comes bundled in the installation package of Apple Inc.’s OS X operating system. It is the default mail management application in OS X. It utilizes SMTP for message sending, POP3 and IMAP protocols for message retrieval, and smime.p7s for message encryption.

2) Mozilla Thunderbird

Description: Same as for Windows.

3) Postbox

Description: Same as for Windows.

On Linux/Ubuntu
1) Mozilla Thunderbird

Description: Same as for Windows.

On Android
1) X509 Tools

Description: X509Tools was developed mainly to provide S/MIME capabilities and X.500 support on Android. This application supports decryption of S/MIME encrypted attachments (smime.p7s), and also can send encrypted emails. Note that this app is not an email client. It can only decrypt messages received by other mail clients.

Some of these applications you might be able to get for free, while others you may have to purchase.

Step 2

In most of the recent operating systems, installing the right program will automatically result in the correct file association with it. You can then launch the .p7s file, simply by either double-clicking or tapping (touchscreen) on the file itself. In case the file fails to open, you can manually try adjusting the settings of your operating system.

Thus, a file with a .p7s extension is basically a cryptographically signed digital message that you are likely to get in your email. For opening it, depending on your particular operating system, you can install one of the software mentioned above, and let it do the work for you.

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