Query from two tables return error

I have one table email.mail.mailusers :

Table "email.mailusers"
Column | Type |
Modifiers | Storage
| Stats target | Description
-------------+--------------------------+---------------------------------------------+--------
--+--------------+-------------
username | text | not
null | extende
d | |
password | text | not
null | extende
d | |
domain_name | text | not null default '
thetradinghall.com'::text | extende
d | |
created | timestamp with time zone | not null default
now() | plain
| |
Indexes:
"mailusers_pkey" PRIMARY KEY, btree (username, domain_name)
Foreign-key constraints:
"mailusers_domain_fk" FOREIGN KEY (domain_name) REFERENCES
email.domainlist(domain_name)

username | password | domain_name | created
----------------+--------------------------------------------------------------+---------------
arnaud.gaboury | XXXXYYYYYY | thetradinghall.com | 2016-02-04
09:48:58.834774+01

admin |XXXYYYYYY | thetradinghall.com | 2016-03-29
09:58:14.599743+02

postmaster | XXXYYYYYY | thetradinghall.com | 2016-03-31
16:36:18.96176+02

----------------------------------------------------------

I have one view email.mail_dir :

View "email.mail_dir"
Column | Type | Modifiers | Storage | Description
----------+------+-----------+----------+-------------
home_dir | text | | extended |
View definition:
SELECT ((mailusers.domain_name || '/'::text) || mailusers.username) ||
'/'::text AS home_dir
FROM email.mailusers;

home_dir
------------------------------------
thetradinghall.com/arnaud.gaboury/
thetradinghall.com/admin/
thetradinghall.com/postmaster/

---------------------------------------------

What I am trying to do: I want the <home_dir> be returned for <username> u.

The query :
SELECT d.home_dir
FROM email.mail_dir d, email.mailusers u
WHERE u.username='arnaud.gaboury';

But it returns:
home_dir
------------------------------------
thetradinghall.com/arnaud.gaboury/
thetradinghall.com/admin/
thetradinghall.com/postmaster/
(3 rows)

It is obviously not what I expect. I am expecting one answer in this case:
thetradinghall.com/arnaud.gaboury/

Thank you for any help. I have been trying with no sucess. Maybe one
solution could be to create a new view with <home_dir> | username as
columns ?

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