Set dovecot with SSL port 995,993

Install Dovecot
Dovecot is POP3/IMAP server which needs MTA like Postfix to work properly.
#aptitude install dovecot-imapd dovecot-pop3d dovecot-common
Dovecot configuration file is located at: /etc/dovecot/dovecot.conf
Before we proceed we need to make some changes with dovecot configuration file. Double check the following entries in the file if the values are entered properly.
Edit the dovecot configuration file using the following command

Edit /etc/dovecot/dovecot.conf file

#vi /etc/dovecot/dovecot.conf
protocols = imap imaps pop3 pop3s
# uncomment this and change to no.
disable_plaintext_auth = no
pop3_uidl_format = %08Xu%08Xv

# PEM encoded X.509 SSL/TLS certificate and private key. They're opened before
# dropping root privileges, so keep the key file unreadable by anyone but
# root.
ssl_cert_file = /etc/ssl/certs/dovecot.pem
ssl_key_file = /etc/ssl/private/dovecot.pem

Look for the line that starts with auth default, before that insert the lines below.

auth default {
mechanisms = plain login
passdb pam {
}
userdb passwd {
}
socket listen {
client {
path = /var/spool/postfix/private/auth
mode = 0660
user = postfix
group = postfix
}
}
}
Now, rename previous auth default to auth default2. If you dont rename this then dovecot server will give you error like multiple instances of auth default.


Now, create a user to test our pop3 mail with outlook:
#adduser user_name
Note: Always create a separate user to test your mail or ftp.
Restart Dovecot using the following command
#/etc/init.d/dovecot restart

Ref.
www.debianadmin.com


create a self-signed SSL certificate for the Dovecot

openssl req -new -x509 -days 1000 -nodes -out "/etc/ssl/certs/dovecot.pem" -keyout "/etc/ssl/private/dovecot.pem"

cd /etc/ssl/private
# chown root:dovecot dovecot.pem
# chmod 440 dovecot.pem
# cd /etc/ssl/certs
# chown root:dovecot dovecot.pem
# chmod 440 dovecot.pem

 Ref.
paulschreiber.com