I had the same set of problems - Could not access email.
This is for the record of anyone searching for the solution -
First I installed Dovecot as explained. I also have exim running - the Services link on the home page shows which services are running - those include Exim and Dovecot along with Apache, MySQL etc.
Then as I tried to log in, I got the error:
Code
Error opening ../data/default_pref
Could not create initial preference file!
/var/local/vmail/data/ should be writable by user emps
Please contact your system administrator and report this error.
The support team replied with this fix:
Code
root@server# chown -R emps:emps /var/local/vmail/data
root@server# chown -R emps:emps /var/local/vmail/attach
This fixed the login issue, but now I could not send email -
Code
Message not sent. Server replied:
Connection refused
111 Can't open SMTP stream.
The support team suggested that I restart Exim and Dovecot, and to isolate the problem to also disable CSF which I had running.
Since I hadn't made any serious changes to the default installed CSF configuration, I first tried by just restarting the 2 services and it worked. I did not need to disable CSF for testing the fix, though this might vary in your particular case.
I think this means it is a good idea, in general (not always) to restart the services that you have made configuration changes to.
Thanks to the support team for quick replies.