Let's create a new user account named user1.

[root@server1 ~]# useradd user1

Give user1 a new password.

[root@server1 ~]# passwd user1

Create user1 mail directory.

[root@server` ~]# mkdir /home/user1/Maildir

Ensure user1 is the owner and group.

[root@server` ~]# chown user1:user1 /home/user1/Maildir

Give owner (user1) read, write, and execute permission,

[root@server` ~]# chmod 700 /home/user1/Maildir 

Use the ls -l (list long) command to ensure user1 is the owner and group owner and the permissions are 700 (drwx------).

[root@server` ~]# ls -l /home/user1
drwx------. 2  user1  user1  4096  Jan 01 00:01  Maildir

Send user1 an email. This is necessary to create the following directories:

• /home/user1/Maildir/cur
• /home/user1/Maildir/new
• /home/user1/Maildir/tmp

If you have not yet enabled encryption:

[root@server1 ~]# telnet localhost 25
Trying ::1...
Connected to localhost
Escape character is '^]'.
220 mail.example.com ESMTP Postfix
EHLO localhost
250-mail.example.com
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
mail from: root@example.com
250 2.1.0 Ok
rcpt to: user1@example.com
250 2.1.5 Ok
data
354 End data with <CR><LF>.<CR><LF>
Hello World
.
250 2.0.0 Ok: queued as 188B012006D
quit
221 2.0.0 Bye
Connection closed by foreign host.

If you have enabled encryption:

Connect using OpenSSL:

openssl s_client 
-connect mail.example.com:587 
-starttls smtp 
-key /etc/pki/tls/private/mail.example.com.key
-cert /etc/pki/tls/certs/mail.example.com.crt

Send the email:

250 DSN
EHLO localhost
250-mail.example.com
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
mail from: user1@example.com
250 2.1.0 Ok
rcpt to: user2@example.com
250 2.1.5 Ok
data
354 End data with <CR><LF>.<CR><LF>
Hello World
.
250 2.0.0 Ok: queued as 188B012006D
quit
221 2.0.0 Bye
closed

Use the ls -l (list long) command to verify the cur, new, and tmp directories were created.

[root@server` ~]# ls /home/user1/Maildir
cur new tmp