问题
It doesn't seem possible to use htmlBodyRenderingOperationWithMessage: when offline (I get the error A stable connection to the server could not be established.). Why is this?
I already have the MCOIMAPMessage stored locally and thought it contained everything necessary to render the message. Is htmlBodyRenderingOperationWithMessage: pulling more data from the server?
回答1:
Methods for rendering of MCOIMAPSession have limited capabilities.
To support offline rendering of message, you should use:
-[MCOIMAPMessage htmlRenderingWithFolder:delegate:]
Use MCOHTMLRendererIMAPDelegate to provide offline data required to render the message.
来源：https://stackoverflow.com/questions/29342382/mailcore-offline-html-rendering