This article applies to customers that utilize Digital Signatures/SMIME for internal emails, and would like to have these items archived with the signatures intact. As described below, it is recommended that these customers configure POP Journaling for their Mimecast account, as opposed to SMTP Journaling.
When using SMTP Journaling, Microsoft Exchange makes a slight modification to the Content Disposition and/or Content Type header lines when it offers the item to the external SMTP Journal address, resulting in such items getting archived with broken digital signatures. Exchange does not do this when using POP Journaling.
When digitally signed emails are uploaded through POP3 Journaling, Mimecast is not permitted to explode such messages to index the message content, and therefore such items CANNOT be viewed correctly via any of the end user applications. The item will be stored as a Passthrough message (RawEmail.eml), and can be viewed as such via the Administration Console by appropriate Administrators.
- End users can forward such messages from the Mimecast Personal Portal, which ensures that the original item will be delivered to the specified recipient as an attachment to the forwarded message.
- When exporting such items via the Administration Console, these items can be viewed correctly.