Mimecast's primary job is to sit between our email server and the outside world to look at incoming messages. If the messages coming in look suspicious, Mimecast will protect you by rejecting or bouncing the message. In the event of a false positive, incoming messages that have been bounced or rejected can be displayed in Mimecast for Outlook.

Mimecast Bounces

Bounced messages have been accepted by Mimecast but cannot be delivered to the next hop or mail server. When this happens, a notification is sent to the sender of the message. Messages may be bounced for a variety of reasons, such as network issues or the mail server otherwise being unavailable.

To view your bounced messages in the Mimecast for Outlook client:

  1. Expand the Bounces and Rejections tab.
    • Note:   If the Mimecast for Outlook client isn't open, click on the Mimecast tab in the ribbon, then click on the Online Inbox icon in the Email Continuity section. 

  1. Click the Bounced Messages menu item.

  1. Click on a message to display its properties. This includes:

    • The message properties.
    • Content.

If you're contacting the IT Helpdesk about a bounced message, we will always want the Bounce Info, so please make sure to take a screenshot of the Bounced Message, and more importantly, the Bounce Info.

Mimecast Rejections

Rejected messages match certain criteria (e.g. they contain a virus signature, or destined to a recipient that doesn't exist). In these instances, no email data is accepted by Mimecast, and rejected messages cannot be retrieved. With all rejections, Mimecast sends a rejection code to the sending mail server, and the mail server should in turn forward a Non-Delivery Report (NDR) to the sender.

To view your rejected messages:

  1. Expand the Bounces and Rejections tab.

  1. Click the Rejected Messages menu item.
  2. Click on a Message to display its properties. This includes:

    • The rejection properties (e.g. rejection type).
    • Triplet information
    • Remote server information.

IT will be interested in the Rejection Properties (the top section), so if you send a snip, please include the top portion.

If you do need any more information on Mimecast On-Hold Messages, don’t forget to check out this article:

How do I check my Held Messages?

If you want to allow senders please see this article:

Adding a Permitted Sender - Mimecast for Outlook