Prohibited E-mail File Attachments

As the popularity and use of email has increased so has the distribution of viruses and spyware/malware through email.   As a result, Western has chosen to block certain file types that windows operating systems have a built in association to auto launch and which are commonly used to infect computer files or compromise security.  This is crucial as it is not just the recipient's computer that becomes compromised, but all computers attached to the network through both the wired and wireless systems.

List of Prohibited File Attachments

The following file types are currently being blocked by the Western mail servers:

.ade, .adp, .app, .asd, .asf, .asx, .bas, .bat, .bin, .chm, .cmd, .com, .cpl, .crt, .drv, .dll, .emf, .exe, .fxp, .hlp, .hta, .hto, .inf, .ini, .ins, .isp, .js, .jse, .lib, .lnk, .mdb, .mde, .msc, .msi, .msp, .mst, .ocx, .ovl, .pcd, .pif, .prg, .reg, .scr, .sct, .sh, .shb, .shs, .sys, .url, .vb, .vbe, .vbs, .vcs, .vxd, .wmd, .wmf, .wms, .wmz, .wsc, .wsf, .wsh.

* The restriction on .rar and .zip files has been lifted. If you receive a message indicating these file extension have been blocked it is because they contain nested file extension that are still restricted. These files will then need to be password protected in order to be delivered.

Understanding the Behavior

Due to the complexity of the email environment message delivery is processed differently if originating from internal or external sources.

Messages Originating Internally

When a prohibited attachment has been blocked, it will not deliver the attachment to the recipient but the message will still be delivered. The sender will not receive any notification that the attachment has been removed. The attachment will be permanently deleted, and there is no way of recovering this file. The recipient will receive a text (.txt) file embedded into the body of the message in place of the removed attachment. This text file will contain the following message:

A file filename.extension attached to this message has been deleted by the University of Western Ontario's mail server because its type has been identified as a possible security risk to you. For more information, please visit (i.e. this site).

Messages Originating Externally

When a prohibited attachment has been blocked, the message is rejected and the senders mail server is provided with the response; "554 5.7.1 Attachments with file extension zip are not accepted."  In addition to the original sender receiving a more timely response the recipient is no longer obligated to follow up with the sender to reiterate our policy on prohibited file attachments. 

How does this affect me?

To bypass the restrictions of the university mail system on attachments use a compression software that provides password protection. Since most of these software programs are on our list of prohibited attachments you will also need to rename the output. As the sender include the original file type and password in the body of the message. For assistance, please contact the ITS Help Desk at 519 661-3800.

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