The artcile applies only for Exchange accounts with Advanced Email Security.

When a contact sends you a message with an attachment, the message may be rejected with the following message:

"Message content rejected."

This will occur even if the message does not contain a virus.

Smarsh Hosted Services Exchange Hosting spam filters block certain attachment types because those attachment types often contain viruses. The current list of blocked attachment types is:

File extension       File type
.ade Microsoft Access project extension
.adp Microsoft Access project
.bas Microsoft Visual Basic class module
.bat Batch file
.chm Compiled HTML Help file
.cmd Microsoft Windows NT Command script
.cpl Control Panel extension
.crt Security certificate
.exe Program
.hlp Help file
.hta HTML program
.inf Setup Information
.ins Internet Naming Service
.isp Internet Communication settings
.js JScript file
.jse Jscript Encoded Script file
.lnk Shortcut
.mde Microsoft Access MDE database
.msc Microsoft Common Console document
.msi Microsoft Windows Installer package
.msp Microsoft Windows Installer patch
.mst Microsoft Visual Test source files
.pcd Photo CD image, Microsoft Visual compiled script
.pif Shortcut to MS-DOS program
.reg Registration entries
.scr Screen saver
.sct Windows Script Component
.shs Shell Scrap object
.shb Shell Scrap object
.vb VBScript file
.vbe VBScript Encoded script file
.vbs VBScript file
.wsc Windows Script Component
.wsf Windows Script file
.wsh Windows Script Host Settings file
.xml Extensible Markup Language file
.docm Microsoft Word macro-enabled file

Note: if the file has double extension, and the second extension is of the following type:

  • .vbs
  • .pif
  • .scr
  • .bat
  • .exe
  • .dll

the file will be blocked.

The content of the following archived files are also being checked by antivirus:

File extension      
.bzip2
.lzop
.cab
.gzip
.arc
.arj
.zoo
.pax
.cpio
.ar
.ripole
.rar

There are a few workarounds:

  • Recommended: Have your sender archive the files as a ZIP file, because *.zip attachments are more likely to be delivered to your mailbox. To ensure delivery, the .zip archive can be password protected.
  • Ask your sender to rename the attachments. You can then save them to your hard drive and rename them back.
  • Note: this feature availability depends on your plan.
    Go to CONTROL PANEL > Services > Advanced Email Security and turn off the option for filtering attachments: set the Accept messages with dangerous attachments option to Everyone.
    However, this is not recommended because you will receive all virus attachments with no filtration.

    A safer solution is to add the sender to your Safe Senders list and then set Accept messages with dangerous attachments to Safe Senders Only:

Notes:

  • Despite the attachment filtering, it is still possible to receive viruses in your mailbox. For example, many newer viruses are sent in encrypted (password-protected) ZIP files, to prevent content and virus filters from detecting them. Even a virus filter cannot filter these viruses, because it does not "know" the password to the ZIP file. Therefore, you should keep an updated virus scanner on your computer, and be very careful about opening attachments. If you decide to open an attachment, save it to your hard drive and have your virus scanner check it before opening.