Go ahead and install dovecot and postfix and configure them.
Not sure what you mean "front end" for dovecot. You just add your configs and start it.
Dovecot of course reads mails from maildir or mbox formats storage and serves it via pop3, imap, pop3s, and imaps.
Your first design decision is whether you want to to us mbox or maildir.
Here is a real quick setup note for postfix+dovecot.
The example uses maildirs (not mbox). You'll want to tweak the domain name, ISP smtp destination, IP address ranges.
You'll need to open ports 25 for SMTP and 993 for IMAPS.
That example postfix stores emails at
home_mailbox = .Maildir/
meaning in ~/.Maildir/
The Dovecot config is to set up an SSL cert, and a single tiny file added to /etc/dovecot/conf.d/11-local-mail.conf containing:
Afte you've done that then you can sent trivial emails to postfix from the postfix server like .....
mail -S "the subject" sepoto@localhost
this is the text
(the final period tels mail the msg body is complete),
Postfix should sent the msg to ~sepato/.Maildir/new/some-aweful-name,sb (I'm assuming you have an account at /home/sepato)
You should be able to connect to dovecot with a goo mail client (thunderbird, evolution) on port 993. You'll have to configure it for imaps (s for ssl) and to use normal password authentication.
When you connect you'll have to tell it to accept the self-signed cert permanently. Then use your password on the server.
Then you should see the email msg via dovecot.
I haven't configured squirrelmail in a long time - but it's the same idea - it needs to connect to the dovecot port 993, and except the home-mae cert, enter the use passwd.