[Dovecot] can not receive external emails

[Daminto Lie]

Hi,

I am new to Dovecot. Recently I have got a new server running on Ubuntu Server 
10.04 with Postfix, Dovecot (for IMAP) and Squirrelmail. During the test, I was 
able to send & receive emails internally, and can send emails externally. 
However, I got a problem when it comes to receiving emails externally. The 
emails I sent from yahoo never arrived to my local inbox. 


Anyway, I checked the mail.log and found the following
dovecot: auth-worker(default): dovecot-auth:  /usr/locallib/liblber-2.4.so.2" no 
version information available (required by dovecot-auth)
dovecot: auth-worker(default): dovecot-auth:   /usr/locallib/libldap_r-2.4.so.2" 
no version information available  (required by dovecot-auth) 

dovecot: auth-worker(default): dovecot-auth:   /usr/locallib/libldap-r-2.4.so.2" 
no version information available  (required by /usr/lib/libpq.so.5)

I was wondering if anyone might be kind to explain the above error messages and 
how to work around this so that it could send/receive emails coming from 
external mail server.

Thank you in advance