Restrictions e-mail attachments

Most viruses and Trojans are spread by malware in e-mail attachments.

For IT security reasons, the following restrictions therefore apply to e-mail attachments:

Size of the attachment

E-mail attachments must not be larger than 30 MB.

File extensions

Emails whose attachments have the following extensions are blocked:

.ace - Microsoft Access
.arj - Archived by Robert Jung
.cab - Compressed archiving of files
.docm - MS Word document format with macros
.dotm - MS Word document format with macros
.exe - MS Executable
.html - Web pages
.img - Apple Disk Image / Raw-Image
.iso - ISO-Image
.jar - Java Archive
.lha .lzh - LHA/LZH Compressed File (from October 2025)
.library-ms - Windows Library Files (from July 2025)
.one - OneNote files
.ppam - Powerpoint with macros
.ppsm - Powerpoint with macros
.pptm - Powerpoint with macros
.potm - Powerpoint with macros
.sldm - Powerpoint with macros
.svg - Scalable Vector Graphics Scalable Vector Graphics
.url - Web address (from July 2025)
.xlam - Spreadsheet with macros
.xlsm - Spreadsheet with macros
.xltm - Spreadsheet with macros
.xlsb - Spreadsheet with macros

Email content

Emails whose attachments have the following content are blocked:

Content-Type: application/ace
Content-Type: application/arj
Content-Type: application/cd-image
Content-Type: application/iso-image
Content-Type: application/iso9660-image
Content-Type: application/java-archive
Content-Type: application/windows-library+xml (from July 2025)
Content-Type: application/x-dosexec
Content-Type: application/(....).macroenabled.(...)
etc.
Content-Type: application/windows-library+xml (from July 2025)
Content-Type: image/cdr
Content-Type: image/x-cdr
etc.
Content-Type: text/uri-list (from July 2025)
Contetn-Type: text/x-uri (from July 2025)

ClamAV finds macros