How to receive a file with a blocked extension type

If a legitimate file that someone sent to you was blocked by a BU mail server, you will need to contact the sender and ask that they modify the file extension — the letters after the “dot” in the filename — to get the file to you.

Modify the file extension
If you need to receive a file of a type that has been blocked, you should ask the sender to rename the file before attaching it to the mail message and sending it to you. For instance, the sender could rename a file from MyProject.exe to MyProject.exeREMOVE. This will allow the file to pass through Boston University central mail servers unmodified. When you receive the message, you can save the attached file to your disk, renaming it back to MyProject.exe (removing the letters “REMOVE”) and then it should function normally. If you are unable to see the .exe or similar file extensions, please follow our related instructions.

Why certain types of attachments are blocked by BU’s mail servers

Infected computers, usually Windows-based PCs, commonly try to spread viruses by sending thousands of messages containing certain types of dangerous attachments through email. Anyone opening such a message (in some cases even viewing just the header is sufficient) will infect their PC with the virus unless some protective measure (e.g., anti-virus software with a matching definition) intervenes to prevent it. If the recipient has no anti-virus software or hasn’t kept the definitions up to date, or the virus is so new that definitions have not yet been distributed for it, the PC will usually be infected.

To help protect people against this type of infection, especially between the time a new virus comes out and the time anti-virus definitions to detect it become available, most large institutions have a policy of blocking certain types of attachments. These types of attachments are commonly used to transmit viruses, but most are not often used by people in the normal course of sending mail.

At Boston University, the central mail servers block the attachment types listed in the table below (i.e., files ending with these extensions) in inbound mail. Note that commonly sent legitimate attachments, such as Word (.doc) and Excel (.xls) documents, are not blocked. Nonetheless, you should exercise caution when opening any attachment, as even Word and Excel files can contain viruses. You should always scan any attachment you receive for viruses before you open it, even if it’s from a trusted source.

Blocked attachment types

File Extension
.bat Batch command file
.cmd Command file
.com Command file
.cpl Windows Control Panel
.exe Executable program
.msi Microsoft installer program
.pif Program Information File, contains information on how Windows should run a non-Windows (e.g., DOS) program
.reg Registration information
.scr Screen saver
.vbe VBScript encoded script file
.vbs Visual Basic script file
Compressed or “zipped” files with a .zip or .gz extension are blocked only if they contain a file with one of the extensions listed above (e.g., a .exe file) or a virus.