Here's the thing I own a small business and currently my emails are being managed by some regular hosting using cpanel and that

I bought a small server and installed windows server and exchange

Can you tell what I did wrong here

1. Installed and configured my current existing domain
2. Configured all email address
3. Installed noip in case my public address change
4. In the cpanel of the domain I've added an MX record to the noip domain of the server with priority 0 so now emails are being received by my own server

Now whenever I send an email to anyone gmail hotmail etc I get a response that cannot be delivered since may be junk

This didn't happen when I sent emails from the hosting

What's missing what did I do wrong

heres the code

mx.google.com rejected your message to the following e-mail addresses:
Joan J. Guerra Makaren ([email protected])
mx.google.com gave this error:
[186.88.202.13 12] Our system has detected that this message is likely unsolicited mail. To reduce the amount of spam sent to Gmail, this message has been blocked. Please visit http://support.google.com/mail/bin/answer.py?hl=en&answer=188131 for more information. cn9si815432vcb.71 - gsmtp 
Your message wasn't delivered due to a permission or security issue. It may have been rejected by a moderator, the address may only accept e-mail from certain senders, or another restriction may be preventing delivery.

Diagnostic information for administrators:
Generating server: SERVERMEGA.megaconstrucciones.com.ve
[email protected]
mx.google.com #550-5.7.1 [186.88.202.13 12] Our system has detected that this message is 550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to Gmail, 550-5.7.1 this message has been blocked. Please visit 550-5.7.1 http://support.google.com/mail/bin/answer.py?hl=en&answer=188131 for 550 5.7.1 more information. cn9si815432vcb.71 - gsmtp ##
Original message headers:
Received: from SERVERMEGA.megaconstrucciones.com.ve
 ([fe80::9096:e9c2:405b:6112]) by SERVERMEGA.megaconstrucciones.com.ve
 ([fe80::9096:e9c2:405b:6112%10]) with mapi; Thu, 29 May 2014 11:32:19 -0430
From: prueba <[email protected]>
To: "Joan J. Guerra Makaren" <[email protected]>
Subject: Probando correos
Thread-Topic: Probando correos
Thread-Index: Ac97V1eW4OBFmoqJTRGoD7IPTC2azg==
Date: Thu, 29 May 2014 16:04:35 +0000
Message-ID: <[email protected]>
Accept-Language: en-US, es-VE
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
Content-Type: multipart/alternative;
    boundary="_000_000f42494487966276f7b241megaconstruccionescomve_"
MIME-Version: 1.0