I'm very sorry you are running into such challenges with this.
Transferring a domain does NOT transfer your site. You have to do the site manually, page by page. The email belongs with and will transfer with a domain. MX It! will work with an existing email account, like Gmail. If you don't have a live email account at NetNation, there is nothing to MX with. I'm not saying this is your issue, just thinking it might be. You could reach out to Support and have them check/test your MX set up but you need a separate email to communicate with them (see my suggestion below).http://support.sitesell.com/contact-support.html
What I would recommend is to transfer the domain back to NetNation so your site and email are working again. You need the site live in order to copy it over anyway.
Then I would do the transfer step by step this way:
1. Set up a temporary domain with SBI!
2. Set up the design you want to use (Pros can usually emulate
an existing design, or prepare a standard new design if you need help).
3. Copy pages/posts over to SBI! using our pagebuilder (BB2). We
could estimate this work after looking at the existing site if you want.
I also recommend you read the Action Guide, and doing it this way
gives you time to do so. Reviewing pages during the move process
will help in seeing which pages need removed and which need
4. Once everything is converted, then move the original domain over
and replace the temporary domain. The site never goes down. Keep
in mind any email attached to your original domain will also move over.
Support (free) gets involved in the domain transfer, and it would require the purchase of one Name Park It! account to do the transfer. Approximately $12 USD.
5. Immediately set up the email accounts in SBI! Webmail to replace
NetNation account(s) OR
6. Set up a secondary domain (similar to your existing original
domain) at NetNation and redirect all the email there (or use
the original for email at NetNation, and the secondary for the
new SBI! site.
Keeping the original at NetNation will change the steps here a bit, #4 and #5 would no longer be needed.
For communication with Pros or SiteSell Support, email is
essential. I suggest you set up a free email account with
Gmail, Hotmail, Yahoo or similar so you can at least
communicate until your domain email is working again.
I know this seems like a lot of work, and it is. But when an existing site is involved, it is best to use a cautionary, slower pace in moving everything.
Please email me and we can discuss this further. debs (at the domain) sitesell.com
All my best,