Actually, I ended up having to implement the config mods detailed in the instructions below. In my case, all attachments were being blocked. It wasn't until I made the suggested edits and restarted the EAS integration service that attachments began to be included w/ the message.
Attachments are blocked by Secure Email Gateway
Feb 5, 2016 3:28pm
An email containing an attachment displays the attachment on a desktop, however, the attachment does not display on a mobile device. Mobile Email Management has been configured using a Secure Email Gateway (SEG).
Perform the following steps to ensure attachments are not being incorrectly blocked:
Verify the SEG Test Connection in the console is successful
Navigate to the SEG server. Open the EAS Integration Service config file (AirWatch X.X/AW.Eas.IntegrationService/AW.Eas.IntegrationService.exe.config by default). Make a copy of this file into a separate directory before making any direct edits. Find the line that contains Allow Attachments and set it to True. You can also alter the maximum size of attachments.
Open the EAS Web Listener config file (AirWatch X.X/AW.Eas.Web.Listener/web.config by default). Make a copy of this file into a separate directory before making any direct edits. Find the line that contains Allow Attachments and set it to True.
Restart the EAS Integration Service for the changes to take effect. If attachments were previously blocked or the maximum size was set too low, attachments should now send correctly.