Am I doing something wrong when I answer a post?

Lets say the subject is "Post Test"

The title becomes

[Freeswitch-users] Post Test

****** When replying, please edit your Subject line so it is more specific
****** than "Re: Contents of FreeSWITCH-users digest..."

So, when i reply, i tried 

Re: [Freeswitch-users] Post Test
Re: Post Test
re: [Freeswitch-users] Post Test
re: Post Test

But it's always create a new thread

I'm wrong?

ps. i'm using gmail

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