I am using mail server on RHEL 5 with Webmail on Squirrel mail and sendmail and found some log. Does it mean any attack on my server?

I have found this log at Mail Server. Does it mean any attack on my server?
 
dovecot:
    Authentication Failures:
        rhost=::ffff:10.50.0.2 : 125 Time(s)
       root: 9 Time(s)
       sales: 3 Time(s)
       adm: 1 Time(s)
       apache: 1 Time(s)
       backup: 1 Time(s)
       bin: 1 Time(s)
       clamav: 1 Time(s)
       daemon: 1 Time(s)
       ftp: 1 Time(s)
       games: 1 Time(s)
       gopher: 1 Time(s)
       halt: 1 Time(s)
       lp: 1 Time(s)
       mail: 1 Time(s)
       mailnull: 1 Time(s)
       mysql: 1 Time(s)
       news: 1 Time(s)
       nfsnobody: 1 Time(s)
       nobody: 1 Time(s)
       operator: 1 Time(s)
       postgres: 1 Time(s)
       rpc: 1 Time(s)
       rpcuser: 1 Time(s)
       rpm: 1 Time(s)
       shutdown: 1 Time(s)
       smmsp: 1 Time(s)
       sshd: 1 Time(s)
       sync: 1 Time(s)
       uucp: 1 Time(s)
    Unknown Entries:
       check pass; user unknown: 125 Time(s)
 
 
 ---------------------- pam_unix End ------------------------- 
 
 
 --------------------- Connections (secure-log) Begin ------------------------ 
 
 
 **Unmatched Entries**
 webmin[14051]: Successful login as root from 10.50.1.6 
 webmin[15142]: Logout by root from 10.50.1.6 
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
staff
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
administrator
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
recruit
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
alias
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
office
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
samba
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
tomcat
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
webadmin
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
spam
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
virus
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
cyrus
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
oracle
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
michael
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
test
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
webmaster
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
postmaster
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
postfix
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
paul
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
guest
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
admin
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
linux
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
user
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
david
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
web
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
pgsql
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
info
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
tony
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
core
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
newsletter
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
named
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
visitor
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
ftpuser
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
username
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
administrator
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
library
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
test
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
admin
 dovecot-auth: pam_succeed_if(dovecot:auth): error retrieving information about user
guest

                                  

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