How Does Large File Send Work?

Document created by user.oxriBaJeN4 Employee on Sep 7, 2015Last modified by user.oxriBaJeN4 Employee on Sep 10, 2018
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Securely sending large files via email is a real problem, and has become a battle between users and IT departments. Seeking to protect overall email system performance, IT teams routinely set limits on email size. File sizes in general are growing, so users often struggle to share vital content with internal and external contacts. 


Large File SendOur Large File Send feature offers a solution by enabling users to safely send and receive files up to 2 GB. The availability of the files are controllable by the administrator, and users can expire links at any time. Attachments are uploaded from the following applications via the Large File Send portal:

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


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. 

The ability to receive files through the Large File Send service requires the configuration of Large File Send Prime or Pro in the Administration Console. See the Configuring Large File Send Prime or Pro page for more information.



The sending and receiving of Large File Send attachments works as follows:

  1. Download Large File SendThe sender composes an email with Mimecast for Outlook, the Mimecast Personal Portal, or Mimecast for Mac, 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 file is 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. The message displays.
  5. The user clicks on the Download Files button and is redirected to the Large File Send portal. At this stage, the user may be required to enter an Access Key to log in to the portal.
  6. Once logged in to the portal, the user can click on either Download or Download All to download the file/s to their local desktop.

Large File Send Portal


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