**File Types blocked in the 2010 Hosted Exchange environment and Outlook**
The file types that are blocked by TrendMicro / ScanMail, for the Hosted Exchange Environment are listed below. These file types are restricted for security purposes and cannot be changed. However, if you .ZIP and password protect the files, they will pass the scanning mechanism on our servers. Make sure not to include the password for the password protected .zip file in the body of the email as the scanning mechanism will catch it and reject the file.
Attachments with these extensions are blocked even if they are zipped but not password protected by ScanMail / TrendMicro:
ADE, ADP, ASX, BAS, BAT, CHM, CMD, COM, CPL, CRT, DLL, EML, EXE, HIV, HLP, HTA, INF, INS, ISP, JS, JSE,MSC, MSI, MSP, MST, OCX, OFT, OVL, PCD, PIF, PL, PLX, SCR, SCT, SH, SHB, SHS, SYS, VB, VBE, VBS, VSS, VST, VXD, WSC, WSF, WSH.
Outlook also has its own filter that is developed by Microsoft and here is a link to the information.
Here is another article on how to unblock Outlook filtered attachments:
Lastly, there is a gui driven program to make changes to Outlook so you don’t have edit the registry.