Without subclassing UIActivity, is it possible to use UIActivityViewController (UIActivityTypeMessage) to share a html message via the Mail app?
When I passed the HTML as NSString, the body shows the html tags (e.g. ) in the message body which is not what I want.
Make sure the string you pass into the activity includes <html. UIKit's internal UIMailActivity class explicitly checks for the presence of <html to determine if the message is HTML or plain text.
[r12 rangeOfString:@"<html" options:NSCaseInsensitiveSearch range:0x0];
Note that while UIActivity is documented that it can send HTML messages, this exact trigger mechanism isn't part of the API contract. Technically, it could break in future versions.
来源：https://stackoverflow.com/questions/19695877/html-email-message-body-with-uiactivityviewcontroller