Attaching Files to email and Calendar Events

Overview

The Campus Mailing List Server does not  manipulate  attachments sent via email .  However, there are a couple of restrictions:

  1. The Campus Email Relays do restrict certain file types.  These types  typically include: executable files, encrypted files and files that can’t be scanned by our security software.   Tech Services does not block Word documents, spreadsheets, PDF files and most graphic files.  More details can be found the KB article, Email, Spam Control, Attachment filters.
  2. The Campus Mailing List Service has a 10MB  “total message size” restriction.  The total message size represents all data associated with the message and includes: the message header (to/from, etc), the body(message) and any attachments.  As with all email, the attachments are MIME-encoded which can more than double the size of a binary file.  To work-around the 10MB limit subscribers can use a file sharing service like:
      • The Campus Drop Box, https://box.illinois.edu/,
      • Google drive, https://drive.google.com
      • And each mail list has a “Shared Documents” directory.  The link is located in the left column of the mail list’s web page.  For example, https://lists.illinois.edu/lists/d_read/LISTNAME/.

Calendar Event Attachments

Many users have notice calendar events behave differently from other attachments.  The Campus Mailing List Server simply passes the attachment as any other attachments and does not manipulate the data or rename the file.  It is the email host (Outlook/Exchange, GMail, Yahoo, Hotmail, etc..)  that defines how they handle the calendar event.

When a user creates a calendar event with Outlook / Exchange, the Exchange server recognizes the ‘internal’ email addresses and provides the extra service of adding a tentative event to the user’s calendar.  However, this is only Exchange to Exchange user behavior and many users consider it default behavior.  When someone sends a calendar event to an email address “unknown to Exchange”,  e.g. a mail list address, then Exchange’s behavior is quite different.   Below we describe the different behaviors when you “create a calendar event and include a list email address in the invitation list”  vs. “attaching a calendar event”  to an email.

Calendar Event Type Outlook/Exchange Gmail Yahoo Mail
Create a new calendar event and invite the mail list address to the event. Outlook renames the calendar event.

However, if you click on the attachment, you will have the accept, reject or tentative options for your calendar.

 Gmail recognizes the event and provides a user interface to add the event to your local calendar. Yahoo recognizes the event and provides a UI to add the event to your local calendar.
Drag-n-Drop a calendar event into an email sent to a mail list Outlook shows the calendar event; an attachment exists but Outlook does not provide options to accept or reject.

The attachment is considered suspect because Outlook doesn’t recognize the mail list email address in the to: or from: field.

Gmail shows the calendar event as an attachment, noname.eml. The email provided a link to an attachment and renamed it to a .txt file.

In summary, there are a few options for sending calendar events to a mail list:  

Option 1) To make sure your invite makes it to “all” the subscribers on your list, regardless of which email client they use, we recommend you add the event information to the body of the message.  This will ensure your subscribers receive the relevant information and they can create the appropriate event on their calendar.  + option 2 for those user’s whose email client’s will provide the add option to their calendar.

Option 2) Add the mail list address to the invitee list and most email clients will allow the user to add it to their calendar.  Most email clients but not all….

Option 3) Worse:  drag-n-drop a calendar event to an email that you’re sending to a mail list.  In this case, most email clients see the attachment as suspect and will rename it, delete it or provide an ascii version of the information in a text file.    

Calendar Event References

Calendar Event Behavior Defined

This document describes the expected behavior of calendar events sent a Campus Mailing List from Outlook, Gmail, Yahoo and Hotmail.

Getting Outlook to recognize 3rd Party Calendar Events (.ics, ical, etc)

There is a registry key a user can set to make Outlook recognize 3rd party / unknown calendar events.   When the key is set to 1 the Outlook will attempt to interpret the 3rd party calendar format so you can accept or reject it.   By default the key doesn’t exist so when the key is set to 0 Outlook will not accept meetings sent by 3rd parties.   

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Key: HKEY_CURRENT_USER\Software\Microsoft\Office\<version>\Options\Calendar 
Value name: ExtractOrganizedMeetings 
Value type: REG_DWORD 
Value: 1

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Below are appropriate registry setting files for the different versions of Outlook.  Simply download the *.reg file for your version of Outlook, double click it and Windows will create the key and enable the ExtractOrganizedMeetings feature.

There are known side effects of ExtractOrganizedMeetings key.  These include:

  1. When booking a room, the meeting is not automatically declined when your time conflicts with another meeting already scheduled.  Double click on the room to see its availability.
  2. A meeting created by a delegate appears on the delegate’s calendar even-though the delegate was not invited.
  3. Updates to a single instance of a reoccurring meeting do not get reflected on the delegate’s calendar.