i am trying to configure **Exchange Server 2010** on **Windows Server 2008 R2** to receive emails from the internet following the **danscourses** tutorials: 

and i followed this video for the DNS & MX records:

<http://www.youtube.com/watch?v=jdf_3DRssks>

i don't have any windows administration skills, and i am stuck with the DNS configuration.
and the following are my domain configuration i got from the hosting.
![My Domain Configuration](https://i.stack.imgur.com/cUF0w.png)

following are the steps i made:

**1- Add new name server:**

add > ns1.centors.com
ip > Exchange Server Public IP: 41.233.26.131

**2- Change the A record**

change it to point to the public ip address > Exchange Server Public IP: 41.233.26.131

**3- New cname record for www** 

and make it resolve to centors.com

**4- New mx record for mail.centors.com**

**5- New A record for mail.centors.com:**

name: mail
ip: Exchange Server Public IP: 41.233.26.131

**6- new A record for ns1:**

ip: Exchange Server Public IP: 41.233.26.131

**7- i made port forward** in the router for SMTP and POP3 to the exchange server local ip address.

**ISSUE:** i have a user account in the active directory, and the user is member of the domain, the user is **myuser@centors.com** and when trying to login with this account in outlook 2010 on other machine using following data:

* **account type:** POP3
* **incoming mail server:** mail.centors.com
* **outgoing mail server:** mail.centors.com

i always get the error: **Authorization failed, check your server settings**.

please advise what's wrong with the configuration, thanks in advance.