Zip files quarantined by Office 365/Exchange

IMSS would like to remind Office 365 and IMSS Exchange users that incoming messages containing .zip files will have the attachment quarantined. This change was made several months ago in response to a marked increase in malicious .zip attachments. If necessary, however, quarantined attachments may be retrieved by contacting the Help Desk (x3500, help@caltech.edu, https://help.caltech.edu) and providing the ID number provided in the Quarantined Attachment notice. Note that Standard Unix email users are unaffected and will not have zip attachments removed. Below is a summary of how mail should be delivered when containing a .zip file:

  Recipient is
Office 365
Recipient is
Caltech Exchange
Zip sent from
outside Caltech, Standard Unix,
(local) IMSS Exchange

 
• Delivered to Inbox
• Quarantined attachment
• Delivered to Inbox
• Quarantined attachment
Zip sent from Office 365 • Delivered to Inbox
• Attachment is included
 
• Delivered to Inbox
• Attachment is included

* Note that messages suspected as spam may be moved to the Junk folder if you opted to automatically filter junk email and/or if you have created inbox rules.

If you have a need to send a .zip file to a correspondent, please use a file transfer service for this purpose, such as Caltech's own local dropbox service (https://dropbox.caltech.edu) for files under 2Gb in size, or the Internet2 Filesender service (https://filesender.internet2.edu/) for larger files. Note that the Internet2 Filesender service requires authentication on the part of the sender, and can be used with access.caltech credentials.