Are you using an outdated version of Word and can't open the DOCX file you received by email? This format was introduced in Word 2007 and is not supported by older versions of Word and other text editors. But converting this format is pretty easy.
Steps
Method 1 of 4: Using the Office XP and 2003 Compatibility Pack

Step 1. Download the compatibility pack from the Microsoft website
This package will allow an older version of Word to open DOCX files. To find the package, go to the Office section of the Microsoft Download Center.
You can download the package for free. We recommend downloading the package only from the Microsoft website

Step 2. Run the installation file
When the download is complete, run the FileFormatConverters.exe file. The package will be installed on your version of Office, allowing you to open DOCX files.

Step 3. Open your document
Once the package is installed, open the DOCX file like any other document. To do this, either double-click the file or open it from Word.
Method 2 of 4: Using a converter

Step 1. Download a converter software or search for an online converter
There are many programs and services with which any document can be converted to DOC format. Popular services are:
- Zamzar;
- Investintech;
- Free File Convert.

Step 2. Download the file
In the case of an online converter, upload the file to the service website. Most of the services are fairly secure, but if you want to convert a confidential document it is best not to use this method.

Step 3. Download the converted file
In a moment, the converted document will be available for download. Depending on the service, the document will be emailed to you, or you will need to click on the download link on the service's website. If you are using a converter program, the file will be placed in the folder for the converted documents.
Method 3 of 4: Using Google Drive

Step 1. Open Google Drive
You can open almost any document format in Google Drive. You can then download the document to your computer in a different format, or edit it directly on Disk. To use Google Drive, you need a Google account.

Step 2. Download the file
Click New> Upload Files in the upper left corner of the page.
An Explorer or Finder window will open and find the file

Step 3. Convert your document
When the file is uploaded to Google Drive, open it and click "Open with Google Docs" at the top of the window. The document can now be edited.
If you don't click Open in Google Docs, you can view the document, but not edit it in Drive

Step 4. Open the file
You will find it in the My Drive folder on the left pane of the Drive page. Click on the file to view or edit it (depending on whether the file is converted).

Step 5. View the converted file
The format of the original document may have changed slightly during the conversion, so review the document to make sure everything looks the way you want it.

Step 6. Download the file to your computer in a different format (for example, PDF or RTF)
Click File> Download As and choose the format you want. The file will be downloaded to your computer.
Complex or fancy text formatting, such as writing words from right to left, is likely to disappear when converted
Method 4 of 4: Using ONLYOFFICE

Step 1. Open the ONLYOFFICE website
It is a free service that you can register for via social media or email.

Step 2. Download the DOCX file
Click "Upload" in the upper left corner (next to the "Create" button). ONLYOFFICE supports DOCX format, so you don't need to convert anything.
An Explorer or Finder window will open and find the file you want

Step 3. Open your document
It will be added to the "My Documents" folder on the left pane of the ONLYOFFICE page. Click on the document to open it in a new window.

Step 4. Edit the document
The ONLYOFFICE interface is very similar to the Microsoft Office interface.

Step 5. Any changes you make are saved automatically

Step 6. Download the file to your computer in any format (PDF, TXT, DOCX, ODT, HTML)
Click on the "File" icon located on the left in the menu and select "Download As". The file will be downloaded to your computer.