SmarterMail's webmail interface isn't able to properly display certain embedded files in things like emails and tasks when they're sent via/created in Outlook (MAPI). The way around this is to simply attach files to these items rather than embedding them within the message or task.
NOTE: For email messages, embedding image files, icons, screenshots, tables, etc. DOES work -- it's only when embedding other file types (Word docs, Excel spreadsheets, etc.) into a message that is an issue.
For example, if you embed a Word document or PDF file in an email message (using Insert > Object), when a SmarterMail webmail user receives the message, the embedded image will appear as a .DAT file attachment.
Another example would be when creating a Task in Outlook (MAPI) and embedding an image in the task details. When you review the task in webmail, or the person assigned the task views it, the image will appear as a .DAT attachment to the task. The image will not appear in the task description in webmail.
This is due to how Outlook encodes these types of embedded files. These embeds are encoded using RTF and SmarterMail has no way to decode an embed with this encryption type. Therefore, SmarterMail sees it as a generic attachment. So, again, the solution is to send these types of embeds as attachments, either in conjunction with the embed or as a replacement for it.