I don't know much about Apache and mod_rewrite, but your rewrite rule

RewriteEngine on
RewriteRule email_member/$ ?rm=email_member
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will never rewrite any URL that has something after it:

http://localhost/email_member/ -> http://localhost/?rm=email_member
http://localhost/email_member/x -> <unchanged>
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I guess you want to expand your rewrite rule:

RewriteEngine on
RewriteRule email_member/(.*)$ ?rm=email_member;session=$1
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... except that I don't know (and am too lazy to look up) the mod_rewrite syntax for capturing and rewriting stuff.