Thank you, Bob!
Guess what? Yesterday, out of all hope, I sent the same newsletter to one of my friends and he received it perfectly well!
I don't know why when I tried sending it to my Hotmail and GMail accounts and I check the email in the same PC I'm working on, it didn't work out.
I send it to another friend and she received it perfectly well too.
But I'm happy now. Even though I still see the text centered when I send it to myself, I know the rest of the people will get it right.