Hello Youseef.
The first solution is best (one shot operation) when you want to change all user's email address from user1@xyz.com to user1@abc.com.
The second solution is best when the requirement is to change email address to different value for different users.
for example -
user1@xyz.com to user1@abc.com
user2@wxyz.com to user2@abcd.com
user3@xyz.com to user1@mnp.com
in this case you have to pass all user's data like below in text file in TO ASCII FILE
Mskeyvalue;oldEmailAddress;Newmail addree
user1;user1@xyz.com;user1@abc.com
user2;user2@wxyz.com;user2@abcd.com
user3;user3@xyz.com;user3@mnp.com
Regards,
C Kumar