One slight problem is that I do not believe we are taking any more dedicated customers at the moment. With a site that has alot of files going back and forth it can be a good idea to have your own server but it depends on the load your site is creating on the server as to wheather you need to upgrade.
I have not encountered that error, I dont have authentication set in my software and I get no failures.
I am guessing that trabulsi.com.mx is your domain name hosted here? Have you tried changing your SMTP port to 26?
Sorry you have not recieved a response to this yet. I have not had this happen so I cannot give an answer that would help. Give a little more time and we will see if someone comes along with an answer.
Yes you can register before getting a hosting account. Yes you can register world wide. No there will be no trouble adding hosting later. And yes, welcome to the family.