Gmail / yahoo threading email including attachment

Is there a way to force gmail / yahoo in threading emails with the same subject?

Here's what happened with the email that i sent.

Yahoo - the second email is combined with the first email 开发者_如何学JAVAincluding the attachment.

Gmail - The second email is empty and no attachment. The body was replaced with "Important mainly because of the people in the conversation."

I am not sure if threading is causing this problem. is there any way to fix this?

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Yahoo and Gmail detect if the e-mail is in the same context. So a similar body, and same subject.

if you make an e-mail more specific (different contents) it should not make it a thread.

But Threading should not cause the loosing attachment problem. You should dig deeper on that, by looking to your own code.

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It is not possible that your contents go away just like that. In Gmail you can disable threaded view in settings, and I am not sure about yahoo, but it should have options for that