Sqlyog: copy table from localhost to remote server without duplicate records
You can copy your table first into a temporary table in your source database, copy that table to the target database, and merge the data there.

That is, in your source database: 

CREATE TABLE emails_temp AS
SELECT 
    * 
FROM 
    emails ;


... copy this table to the target database using the Copy Database functionality; and drop it from the original:

 DROP TABLE emails_temp ;


Once you have your temporal table at the destination, add the new data to the existing table, doing something like:

INSERT INTO emails
SELECT 
    * 
FROM 
    emails_temp
WHERE 
    primary_key NOT IN (SELECT primary_key FROM emails) ;


(Obviously, you have to substitute primary_key by your actual PRIMARY KEY).

Or you can use also INSERT IGNORE.

After you have transferred all the new rows, you can

DROP TABLE emails_temp ; -- At the destination database