Email message size limits

At Indiana University, the limit on all outgoing or incoming email messages (including their attachments) is 50 MB. Messages larger than this will not go through IU email systems (including Exchange), and attempting to send such messages will result in either an error message from your email client or a non-delivery notice from IU.

Notes:
  • For IU List, the default size for messages is 64 KB. List owners can modify this, up to the maximum of 10 MB, from the list's campus web interface. Select Edit List > Config > Sending/receiving setup > Maximum messages size.

    For campus domains that have been migrated as part of the 2021 IU List upgrade, the limit is 10 MB.

  • For ActiveSync, the method most mobile devices use to connect to Exchange, the size is limited to 10 MB. Some devices and programs have their own built-in limits that may reduce this further.
  • For Outlook Web App (OWA), the size is limited to 25 MB.
  • For messages encrypted by CSEES, the maximum size, including attachments, is 10 MB. If a message exceeding that size is marked for encryption, it will be returned to the sender with the subject "[ENCRYPTION FAILURE]". See About the Cisco Secure Email Encryption Service (CSEES).

The 50 MB limit reflects the size supported by IU's email environment. However, some organizations outside of IU will reject messages above 8-10 MB. When sending email messages to non-IU addresses, you may wish to further reduce your message size:

  • Large or multiple attached files are the main reason that email messages exceed the maximum size limit. Though unlikely, it is also possible that the text of the message is too large. Remove attachments or edit the message until it is less than the maximum size. Alternatively, break it into several smaller files that individually do not exceed the limit.
  • Use a file compression utility to compress a large attachment into a smaller one, or to divide one large file into several smaller files you can then send separately. Both Windows and Mac operating systems have built-in compression software. Third-party compression utilities also exist (some free, some not), and include 7-Zip for Windows, and DropStuff and StuffIt Deluxe for Macintosh.
  • Rather than sending email, you could use a cloud storage option (see Options for storing files at IU), and then give the recipient the URL for the file.
  • Graduate students, faculty, and staff can use the Slashtmp service to temporarily store and share large files via a web interface.

  • Use a third-party freeware or shareware file transfer or chat program to transfer the file to your recipient. These are widely available from software download sites.
  • If your recipient has a network drop box, see if you can place your file there. There are a variety of methods to create a drop box, including anonymous FTP and Mac or Windows file sharing.
  • If both you and your recipient have accounts on the same Unix computer system, you can temporarily set the file permissions so that your recipient can access and copy it. For information about changing file permissions, see Manage file permissions on Unix-like systems.
  • Removable storage devices, such as flash drives or MicroSD cards, can hold a large amount of information. For very large files, the most practical way of transferring information might be to copy the files to such media, and then hand deliver or ship the media to your recipient.

This is document atfi in the Knowledge Base.
Last modified on 2021-04-08 16:22:57.

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