Download of large attachments by VMware Boxer may fail in some Exchange environments

Customers migrating from native applications to Boxer may discover that large attachments may fail to download in Boxer or Inbox, despite being able to successfully download them in the native e-mail client.

  • When attempting to download an attachment above a certain size, Boxer will report that the attachment is too large.
  • The MaxAttachmentSize provisioning policy is set to allow an attachment of that size to download.
  • Examining network traffic will reveal that the request to download the attachment (an ItemOperations ActiveSync command) returns a status of 11, indicating that the attachment is too large.
  • The native iOS Mail application may still succeed in downloading mail.

 

The root cause of this is that the IIS setting for MaxDocumentDataSize is configured lower than the size of those attachments. This setting is independent from the MaxAttachmentSize provisioning policy, and should ideally be set to at least the size configured for that policy.

iOS Mail receives the same error, but also implements a fallback operation using the Sync command (which is not subject to the MaxDocumentDataSize setting) to fetch the entire MIME-encoded message. It can then parse the attachment from the MIME-encoded message.

This works, but has serious drawbacks in terms of bandwidth usage. First, the MIME-encoded message could include multiple attachments - end-users might need just a single small attachment, but will have to also download other attachments in the message, which could be quite large. Second, because the attachment will be download in MIME-encoded format, it will have a 10-15% encoding overhead as well.

 

Resolution

 

Support Contact Information

To open a Support Request, please call your local AirWatch support line or submit a Support Request via myAirWatch.

Best Regards,

The AirWatch Team

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