CentOS 6 - sendmail & dovecot , username or password invalid.

http://prdownloads.sourceforge.net/webadmin
http://prdownloads.sourceforge.net/usermin
yum install webadmin usermin
yum install sendmail sendmail-cf
Issue Resolved
Removed Sendmail and installed Postfix and the settings are here for Dovecot 2.x
POSTFIX Mail Server in RHEL 6:
Postfix Mail Server:
Note: Make sure DNS Server is properly configured.
Install Required package:
# yum install -y *postfix* *dovecot*

Edit postfix configuration main.cf located in /etc/postfix
# vim /etc/postfix/main.cf
inet_interface = all
# inet_interface = localhost
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
home_mailbox = Maildir/
# service postfix start
Note: Dovecot configuration files are located in /etc/dovecot and /etc/dovecot/conf.d
# vim /etc/dovecot/dovecot.conf
protocols = imap pop3 lmtp
# vim /etc/dovecot/conf.d/10-mail.conf
mail_location = maildir:~/Maildir
# vim /etc/dovecot/conf.d/20-pop3.conf
pop3_uidl_format = %08Xu%08Xv
pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
# vim /etc/dovecot/conf.d/20-imap.conf
imap_client_workarounds = tb-extra-mailbox-sep delay-newmail
# vim /etc/dovecot/conf.d/10-auth.conf
disable_plaintext_auth = no
# service dovecot start
To list all protocols listing TCP.
# netstat -at
This website is http://www.wtuto.com
The uploader Mr.Wali Alam is a talented individual .......
The link -
http://goo.gl/uxy8e
This resolved my issue for email server
I feel sendmail and postfix are conflicting and dovecot 2.x doesn't work fine with sendmail .