I am using email-to-case services of Salesforce.
If I receive any case having attachment it gets stored under attchments properly,
But when I open the perticular case from activities to see inbound message, I can see attachments getting converted into html file.
1 answer
See article below, this explains why attachments are being converted to HTML:
https://help.salesforce.com/articleView?id=000326717&type=1&mode=1