eregi("\n", $youremail) becomes preg_match("/\n/", $youremail).

But personally, I'd replace this:

!eregi("\r",$youremail) && !eregi("\n",$youremail)
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With this, because strpos is faster than a regexp:

strpos("\r",$youremail)===FALSE && strpos("\n",$youremail)===FALSE
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Or even (it'll probably be faster, but it's slightly obscure):

strpos("\r",$youremail)===strpos("\n",$youremail)
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