beginner postfix Dovecot squirrelmail clamav

This seem like the right place to put this as it is an email server that I'm trying to do for fun.

links I have used
http://cosmolinux.no-ip.org/raconetlinux2/mail.html
https://help.ubuntu.com/community/Squirrelmail

I need the mail to be sent out by gmail. I have a free dynmic dns with noip.com. I can not seem to find an up to date guide for this. I was able to install postfix well when I say install I mean I think it was down right. Dovecot I did the apt-get install dovecot-postfix so I think it was done right. and as for squirrelmail I have do idea because my page says https://192.168.56.3/squirrelmail/sr...cure_login=yes and it is not working. after I use http://ip or domian/squirrelmail

As for the mail user I want to use the users on the ubuntu computer.