Recently we have had several customers mentioning that there attachments are removed on the recipient end and instead a Winmail.dat file is found attached. Many have contacted us asking if this was due to one of our Outlook addins so we decided to do some research on this. NO!
It turns out that this is a long standing problem between Outlook and Internet email.
Outlook uses an email format that Outlook and Exchange (and MANY other email clients like gmail) can recognize. However some email clients (including unfortunately the IPhone and IPad mail clients) have problems displaying these emails properly.
If you send a email with Attachment to a user of an email program that has problems with Outlook emails, then the recipient gets a plain text message and an attachment called winmail.dat. Any attachment that you might have sent with the email is encased in the winmail.dat attachment.
For those who receive a Winmail.dat file, you will need a tool/utility in order to extract the attachments from the Winmail.dat file (you can easily find a free tool using Google Search).