Problem opening Usermin Inbox

Hi,

My client just install Centos7 and provided me with server access. I installed webmin and virtualmin then configure it to use for a domain...

Now problem is when I check usermin of main domain email id it showing the error

An error occurred listing mail in this folder : Failed to login to POP3 server : Internal error occurred. Refer to server log for more information

[root@mail lib]# netstat -lnp |grep :110 tcp 0 0 0.0.0.0:110 0.0.0.0:* LISTEN 20630/dovecot tcp6 0 0 :::110 :::* LISTEN 20630/dovecot

I check online my open ports and it is showing PORT STATE SERVICE

20/tcp closed ftp-data 21/tcp closed ftp 22/tcp open ssh 25/tcp open smtp 53/tcp open domain 80/tcp open http 110/tcp open pop3 143/tcp open imap 443/tcp open https 587/tcp open submission 993/tcp open imaps 995/tcp open pop3s

I tried adding mail location (currently it is not in /etc/dovecot/dovecot.conf but still failed to remove that error

I check logs and got this error:

dovecot: pop3-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=217.12.123.30, lip=217.12.123.30, secured, session=<EB/U5qdFfgDZDHse> Jan 9 13:45:18 mail dovecot: pop3-login: Login: user=<bounce.topkuv>, method=PLAIN, rip=217.12.123.30, lip=217.12.123.30, mpid=13929, TLS, session= Jan 9 13:45:18 mail dovecot: pop3: Error: user bounce.topkuv: Mail access for users with UID 501 not permitted (see first_valid_uid in config file, uid from userdb lookup). Jan 9 13:45:18 mail dovecot: pop3: Error: Invalid user settings. Refer to server log for more information.

Kindly help me on this.. If required access, I can provide it.

Thanks Kishan Giri