[am]king ~/a/tm$ cat emails
user01 user01@emailaddress.com
user03 user03@emailaddress.com
user04 user04@emailaddress.com
[am]king ~/a/tm$ cat names
user01
user02
user03

##</code><code>##

[am]king ~/a/tm$ sort -k1 emails > emails.sort
[am]king ~/a/tm$ sort -k1 names > names.sort

##</code><code>##

[am]king ~/a/tm$ join -v1 -o0 emails.sort names.sort
user04