Large File Send - Overview

This article gives an overview of the functionality, benefits and known incompatibilities of Large File Send, and is intended for use by Administrators.

Introduction

Large File Send enables your users to send or receive large files directly through Mimecast, when composing emails using: 

• Mimecast Personal Portal.
• Mimecast for Outlook.
• Mimecast for Mac.

Once configured, your users can safely send and receive attachments up to 2 GB in size, via the Large File Send Portal.
You can control the availability of the files as an administrator, and users can expire links at any time.

If messages are sent to a distribution list via Large File Send, users with delegated access to the distribution list are not able to see the message in the archive.
This is because Large File Send sends a notification to each member of the distribution list, not the list's email address.

Before delivery, files are scanned by Mimecast for malware, and may be passed through attachment rules using Attachment Management policies, and Content Examination definitions, depending on your commercial package. These attachments bypass the organization's email server and therefore do not take up storage space.

Considerations 

Mimecast for Mac only supports Large File Send on macOS 10.15 (Catalina) or lower.

How Large File Send works

Sending emails to more than 99 recipients at once using Large File Send can cause delivery problems. To avoid this, limit your list to 100 users. Even then, it’s better to break the list into smaller groups. Large recipient lists might be seen as bulk sending and could end up in the SPAM folder.

Sending and receiving of Large File Send attachments works as follows:

1. The sender composes a message using a Mimecast end-user application, using the applicable Large File Send feature.
2. When the message is sent, the attachments are uploaded through an encrypted channel to the Large File Send portal. During the upload process, the files are transferred in chunks. If the uploads are paused and resumed at a later stage, or if the transfer is interrupted due to connectivity issues, the partial transmission can be resumed from where it left off, or an auto-resume process will activate once connectivity has been restored.

   At this stage, the email passes through any configured policies as described above, and the original email is stored in the archive for the retention period of your Mimecast account.

3. The recipient receives an email notification, which is made up of the original message, and the attachment.
4. The user clicks on the file to open it as normal, and message is displayed:
   
5. The user clicks on the Download Files button and is redirected to the Large File Send portal:
   
6. Once logged in to the Large File Send portal, the user can click on either Download or Download All to download the file/s to their local desktop.
7. If the sender also selected the Large File Receive feature, then the recipient sees an additional button in the email notification:
   
8. The user clicks on Upload Files, and is redirected to the Large File Send portal, which allows the user to Add Files, then Send them to the sender:
   

The user may be required to enter an Access Key to log in to the Large File Send portal (this depends on whether the sender enabled this option).