Content-Transfer-Encoding

We are using Outlook Small Business Ed. 11.5608.5606 and recently all emails that we are sending have two files attached to them. ATT00XXX.txt and ATT00XXX.htm. (content-transfer encoding files) The default setting for email format is HTML and that is what we are using. If we change this to Plain text, the attachment issue goes away. Why is this happening after 8 months using the default setting with no issues.

 

Check one of your sent messages. Does it match the picture below?