Email text not in html form

[rabbitXDD]

After receving email, find that some text not in html form.
For example, some supposed to be:
aaaaaa click here。

'

show in email like this:
<div id="links"> <a name="links"> <p> aaaaaa<a href="http://example.com/newsletters/asd/1-4abbf2734d0590ca4b42/"\>click here</a>。 </p> </div>

It seems like some html content not treated as html at all when processing to generate email.