Odd Characters in Returned emails

Hello, I'm a Newby and not very computer literate !

Do you think a solution can be found for the odd keyborad characters appearing in emails I send to others. It looks fine when I send it and when they receive and send it back email has odd characters in there where I have put punctuation marks like Hyphen, exclamation marks or apostrophe,

This doesn't happen with everyone, just a few people who may be using some sort of webmail but should it happen at all ?

Someone has suggested it is a unicode problem when I set it up. Does anyone know what unicode setting I should have for Windows Live Mail using Windows 7 on a Sony Vaio 64 bit laptop. This also happens in BT Yahoo mail

Here are a few cut and pastes of the problem...........1) mainly exclamation marks the 2nd was just a simple apostrophe in don't.......

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>>>>wouldn’t
>>>>mind trying it one day.
>>>>

I don’t expect you the

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Hope someone can help - thank you.