Canceling the sending of a queued email in Gmail for Android How do I cancel the sending of a queued email in Gmail (Android)?
The conversation is in the outbox and I don't see an option for deleting the message alone. I'd like not to have to delete the whole conversation.

I am temporarily in China where Google is blocked and I want to rewrite an email I had written and tried to send.
I didn't try Matthew's solution but it seems the safer solution to try first. 

If that doesn't work though, I deleted the entire conversation from the outbox, having given up on trying to keep the conversation. I was surprised to find that this only deleted the queued message. The rest of the conversation stayed intact in my inbox.