Question: In an IP Multimedia System (IMS) Messaging context, if a User Equipment (UE) receives a text message with an unrecognized subtype of "text" but with a known character encoding (charset), how should the UE's MIME implementation handle it?
Option 1: Treat it as "application/octet-stream"
Option 2: Ignore the message due to unrecognized subtype
Option 3: Attempt to convert it to a known subtype before rendering
Option 4: Treat it as subtype "plain" since the charset is recognized
Explanation: According to IMS Messaging media formats and codecs specifications, if the MIME implementation recognizes the charset of an unrecognized "text" subtype, it should treat that message as if it were of subtype "plain". This ensures compatibility and maximizes the chances of correctly displaying the text content to the user.