I suppose your aim is to query both of your tables without using mysql_query twice. You'll first have to know which fields connect your two tables. If I'm understanding your problem correctly, these two fields would be user_id and email_receiver_id?
If this is the case, your query should look something like that:
[FONT=Courier New]SELECT * FROM
table_prefixed_with_user
LEFT JOIN (table_prefixed_with_email) ON(user_id = email_receiver_id)
[/FONT]
Additionally, if your goal is to rename the columns' names then replace the * in the query with:
[FONT=Courier New]email_title AS email title[/FONT], etc. (separated by commas)
I'm not sure though, if aliases (the identifiers after AS) are allowed to contain spaces... Also be aware that you'll still have to use the original column names in your WHERE statement otherwise use the HAVING statement for checking values of the aliases...