K2- Activation Link won´t send

So....I installed the template and all works fine!
But when I got to the registration form and fill it out completely and send it , there will no mail will come to the costumer .
What I tried to now:

1.Changed sendEmail to = ´1´ and Deactivate = 'NULL' on the default of the table xy_users (phpmyadmin)
2.Sendemail on Global Config. to "/usr/sbin/sendmail -t -i" like in the PHP Info showed
3. Tried SMTP with following settings:

Mailer: SMTP Server
Mail from: xxxxr@tpg.com.au (this is my email sent from the server to the person who includes their contact email address)
From Name: Fred Bear (this will be what I want to appear in the 'From' of my email)
Sendmail Path: (Leave blank)
SMTP Authentication: (choose No)
SMTP Sercurity (choose None)
SMTP Port (choose 25)
SMTP Username: (leave blank)
SMTP Password: (leave Blank)
SMTP Host: mail.tpg.com.au (add your normal email host. As mine is not on my server my host is not localhost but the email provider that I normally use.)

4. Tried the normal use with PHPMail

But non of it will work , what I´m doing wrong ?
Thanks

Are you maybe on IIS (winodws) in that case that will work only for j3

My host works with Linux and I have joomla 3 installed.
I Asked my host and He said that the Mails where send out, but there don't Come to costumer Who wants to Register.

So the Mail where sand out but they Are Not in the inbox of for Exemple an @gmail.com Account

What could it be?

End up in to spam?

EDIT:

you can open account for sending emails here : www.mandrill.com

You have limit 12000 emails per month after that its payed.

It will tackle many problems for you .

You are the best Mandrill is an awesome service!
Thanks
At first it doesn´t worked but after an Installation of the exstension CMandrill all worked fine.
Bye

Again nothing works ...
So this time is the problem that every time i try to login or to registrate i just got redirect to the homepage and an mail wasn´t send out , also the user is not to see in the user manager backend...

What is wrong now?