Long story short, I have everything working in my SOHO which would include Postfix,Dovecot(imap),Roundcube and is read to recieve email from the outside using this tutorial:

https://workaround.org/ispmail/wheezy

I also setup my internal DNS server using:

https://wiki.debian.org/Bind9

My questions are:

1 - How do I tell godaddy dns servers (mx record) to send email to my domain imap.blah.com?

2 - Is there any thing special I need to do on my end via bind9?

essentially I just need a quick how to in getting this going. So my goal that I am trying to achieve is.

1 - Allowing my employees the ability to be able to check their email from any location via roundcube. Ex. https://blah.com/roundmail

2 - If not using webmail then being able to configure a email client (thunderbird or evolution) via imap.blah.com TCP:IMAP:143/SMTP:25 to be able to recieve and send email.

All help is most appreciated.

Then congrats are in order
It's not actually Go-Daddy that controls that. You need to change the DNS->MX record for your domain to reflect your gateway IP.
The good news is Go-Daddy has tools on your domain page to do that.
The bad news is it doesn't happen immediately, so you're looking at a long cycle of test/modify/test/modify if your mail server isn't properly configured.
As far as I know, not for the mail server. Just make sure your gateway forwards all traffic on POP and IMAP ports to the internal ip it's sitting on. I always harden the crap out of them and put them in highly restricted DMZ. It's wise to harden your gateway as well, nothing like a new MX record for bringing the wannabe hackers to your door. They'll run bots over your gateway looking for open ports and try to exploit anything they find, in a well run environment, they're mostly just a nuisance (like every other variety of poorly raised child).

1 members found this post helpful.

Many thanks for your reply. Actually I forgot to mention that I want to give my users that ability to access their roundcube webmail from wherever they are. So essentially, I am hosting the companies website here as well and want to also allow access the company web-mail like:

https://www.blah.com/roundcube/login.php

Having said that, will I also have to point my domain to my web server from Godaddy so it can be accessible in that manner?

Yup,
Which makes it doubly important you harden your gateway and get highly restrictive DMZ in place. Make sure you've patched all the packages (not just the kernel) in the stack for both servers, but in particular they like to jam up web servers. Make sure you change all default passwords, be especially cautious about PHP administrative tools for the web server and the MySQL database (if you're using one in conjunction with the server) and just a final suggestion, keep yourself mirrored to the Go Daddy site for a month or so before you fly totally solo. That way if you get penetrated, you can fall back to the previous site ( You just flip the DNS records back to the Go-Daddy site) while you work out what happened and fix it.

should I also have my dns server forwarding any unknown request "{forward ....} area of my named.conf.options file ) to godaddy dns servers and also on Godaddy DNS area under my account so they can talk to each other (zone transfer) or is that over kill?

Dude, if you think it's going to help, do it. I'd put fifty cal emplacement on port 80 and 8080 if I could figure out how to virtualize it. When it comes to vermin, no such thing as overkill.

Your DNS server is irrelevant to the rest of the world.
It only provides lookups for clients on your internal LAN.

It points to your internal service records, which isn't trivial if someone is trying to exploit you.