To use the fuctions only if the user allows them to (i.e the email link will only show if the user has let people contact them via the email you will need to use IF conditionals.
Code:
<if condition="$show['pmlink']">
<a href="private.php?$session[sessionurl]do=newpm&u=$post[userid]" rel="nofollow"><phrase 1="$post[username]">$vbphrase[send_private_message_to_x]</phrase></a>
</if>
<if condition="$show['emaillink']">
<a href="sendmessage.php?$session[sessionurl]do=mailmember&u=$post[userid]" rel="nofollow"><phrase 1="$post[username]">$vbphrase[send_email_to_x]</phrase></a>
</if>
That should do it though.
I have only tested with postbit legacy but should work with regular postbit as well.
Connor