Blocking security-critical file formats for e-mail attachments

Since 16.03.2020, the receipt of e-mails with security-critical file formats in the attachment has been prevented by the mail server. The following file formats are affected by this:

1. Macro-enabled Office files

    Word: .doc, .docm, .dot, .dotm
    Powerpoint: .potm, .ppa, .ppam, .ppsm, .ppt, .pptm
    Excel: .xla, .xlam, .xls, .xlsb, .xlsm, .xlt, .xltm

    The lock can also affect data formats based on .doc formats, for example
    Autodesk Inventor files (IPT and IAM).

2. Encrypted .zip archives in unencrypted emails

In both cases, the mail server will reject receipt and send the sender an error message indicating the excluded file format.

A permissible and recommendable workaround is for the communication partner to send you the Office file in a current and non-macro-capable file format (.docx, .pptx, .xlsx). The file format can easily be changed by the user via the "Save file as..." dialogue.

Instead of sending encrypted .zip archives by e-mail to exchange confidential information, you can also store the encrypted file in a CloudStore directory and send a link to your communication partner via the corresponding CloudStore function. You can find a description of our CloudStore service CloudStore service on our web pages.

These protective measures are recommended by the Federal Office for Information Security (BSI) and have already been implemented in large parts of the state administration (including the MWK).



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