I can't log in on thunderbird or evolution

Hello everyone
the server is fedora 17
i'm using sendmail and dovecot servers but i can't log in to use any email account. when i try to log in on thunderbird or evolution, shown me the username is password is error. I am sure the username and password are correct.  dovecot provides access to the mail storage using IMAP

geting this errors

[root@server dovecot]# newaliases
/etc/aliases: 76 aliases, longest 10 bytes, 773 bytes total
[root@server dovecot]# tail /var/log/maillog
May 17 06:31:37 server sendmail[26598]: r4HAVbLc026598: domainname.ex [192.168.105.1] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
May 17 06:31:37 server sendmail[26599]: r4HAVbNj026599: domainname.ex [192.168.105.1] did not issue MAIL/EXPN/VRFY/ETRN during connection to MTA
May 17 06:31:37 server dovecot: imap-login: Aborted login (no auth attempts in 0 secs): user=<>, rip=192.168.105.1, lip=192.168.105.1, secured, session=<JTDnfOfciwDAqGgB>
May 17 06:32:02 server dovecot: imap-login: Disconnected (auth failed, 3 attempts in 20 secs): user=<amanda>, method=PLAIN, rip=192.168.105.1, lip=192.168.105.1, secured, session=<XlAzfefclgDAqGgB>
May 17 06:32:21 server dovecot: imap-login: Disconnected (auth failed, 3 attempts in 19 secs): user=<amanda@domainname.ex>, method=PLAIN, rip=192.168.105.1, lip=192.168.105.1, secured, session=<r85XfufclwDAqGgB>
May 17 06:42:09 server dovecot: log: Warning: Killed with signal 15 (by pid=1 uid=0 code=kill)
May 17 06:42:09 server dovecot: master: Warning: Killed with signal 15 (by pid=1 uid=0 code=kill)
May 17 06:54:37 server dovecot: master: Dovecot v2.1.16 starting up (core dumps disabled)
May 17 06:58:19 server sendmail[26816]: alias database /etc/aliases rebuilt by admin
May 17 06:58:19 server sendmail[26816]: /etc/aliases: 76 aliases, longest 10 bytes, 773 bytes total

please any help...