To block all attachments in Outlook emails, please do as follows:

1. Press Win + R keys simultaneously to open the Run dialog box, type regedit into the Open box, and click the OK button.

2. In the User Account Control dialog box, click the Yes button.

3. In the Registry Editor window, please open the Security key with below path:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security
Note: Above path works for Outlook 2016. Please change the 16.0 in above path to 15.0 for Outlook 2013, or change to 14.0 for Outlook 2010.

4. Right click the Security key, and select New > String Value in the right-clicking menu. See screenshot:

5. Name the new string value as Level1Add.

6. Right click the new Level1Add string value, and select Modify in the right-clicking menu. See screenshot:

7. Now the Edit String dialog box comes out. Please paste below file extensions into the Value data box, and click the OK button. See screenshot:
.xlsx; .docx; .pptx; .pub; .xlsx; .docm; .pptm; .txt; .xlsm; .doc; .ppt; .ps; .xls; .dotx; .pdf; .xps; .xml; . dotm; .xps; .wtf; .mht; . dot; .potx; .emf; .mhtml; . pdf; .potm; .wmf; .htm; . xps; .pot; .gif; .html; . mht; .thmx; .jpg; .xltx; . mhtml; .ppsx; .png; .xltm; . htm; .ppsm; .tif; .xlt; . html; .pps; .bmp; .txt; . rtf; .ppam; .wmf; .xml; .txt; .ppam; .emf; .xls; .xml; .xml; .rtf; .csv; .odt; .mp4; .pptx; .prn; .wrg; .wmv; .odp; .dif; .xlam; .xlsx; .xlam; .slk; .pdf; .ods; .xps; .zip; .rar

Note: Most of extensions used in normal Outlook work are listed here. If you want to block other types of attachments, please add their extensions into the Value data box, and separate them by semicolons.

8. Restart your Outlook.

And now you will see all kind of attachments are blocked in Outlook emails. See screenshot:

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