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I have installed MS Exchange 2016 in my lab.


I can send emails internally just fine but not able to send emails externally.


My AD Domain: Domain.com

My Public Domain: DomainInc.com.au


Error message I get when I send emails externally meaning to gmail, aol or yahoo:


Generating server: EXCH-SRV01.domain.com

Remote Server returned '400 4.4.7 Message delayed'

Original message headers:

Received: from EXCH-SRV01.domain.com (10.X.X.X) by EXCH-SRV01.domain.com (10.X.X.X) with Microsoft SMTP Server (TLS) id; Sat, 27 Feb 2016 04:56:17 -0800Received: from EXCH-SRV01.domain.com ([::1]) by EXCH-SRV01.domain.com ([::1]) with mapi id 15.01.0225.041; Sat, 27 Feb 2016 04:56:17 -0800From: Exchange Admin Account <adm_exchange@domain.com>To: username@aol.com username@aol.comSubject: testThread-Topic: testThread-Index: AQHRcV47KRzLbFmdUEagAG9gVscc+A==Date: Sat, 27 Feb 2016 12:56:16 +0000Message-ID: <5c6080469f5a41c3b2e8bc8be3a3d88b@genesys.com>Accept-Language: en-USContent-Language: en-USX-MS-Has-Attach: yesX-MS-TNEF-Correlator:x-originating-ip: [10.X.X.X]Content-Type: multipart/related;	boundary="_004_5c6080469f5a41c3b2e8bc8be3a3d88bgenesyscom_";	type="multipart/alternative"MIME-Version: 1.0

I have registered a domain with crazydomains and also purchased a dns and email address to verify my domain for SSL certificates.


Created an A Record : mail.domainname.com.au --> pointing to my public domain ip address.

Created another A Record: autodiscover.domainname.com.au --> pointing to my exchange server EXCH-SRV01.domain.com (AD Domain)

Created an MX record: mail.domainname.com.au --> pointing to mail.domainname.com.au


My SSL Certificate has the following under Subject Alternative Name:


DNS Name=mail.domainname.com.au

DNS Name=autodiscover.domainname.com.au

DNS Name=domainname.com.au




Is this configured incorrectly?


I have been stuck with this for a while and tried many google searches to find a resolution with no luck.


Any help would be appreciated.



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Just wanted to share this with others that may have this issue (I was scratching my head for over 2 weeks)


Finally I got it to work. Thanks for the RDNS tip Saligia.


I haven't fully configured everything. Just wanted to get inbound and outbound mail going for now (internal and external), so here is what I did to get it working


1. Got my ISP to provide me with Reverse DNS --> Pointing to mail.publicdomain.com.au (Public domain: IE: Godaddy, Crazydomains and etc)

2. Logged in to my Public domain providers site and performed the following (Note: You may need to purchase DNS Premium service - I did! )

3. In the DNS section:

- Created A Record: Mail.publicdomain.com.au --> pointed it to my public IP address (if you don't know login to your router or call your ISP)

- Created CNAME Record: autodiscover.publicdomain.com.au --> pointed it to mail.publicdomain.com.au

- Created MX Record: publicdomain.com.au --> pointed it to mail.publicdomain.com.au

4. Logged in to my router and added 2 port mappings:

- WAN and LAN Port: 443 (HTTPS) This will allow you to access OWA from outside of your organization/domain

- WAN and LAN Port: 25 (SMTP)

(Hopefully your ISP allows port forwarding)

5. In your Domain Controller or wherever you have a DNS server installed open it up and create an Mail Exchange (MX) record under DC---->Forward Lookup Zones----->Contoso.com.

- Right Click Contoso.com and click New Mail Exchanger (MX).

- Host or child domain: put in your exchange server hostname (IE: exch-srv001)

- FQDN: exch-srv001.contoso.com

- FQDN of Mail Server: mail.publicdomain.com.au (or dot com or whatever you have purchased)

- Mail Server Priority: I kept it as default (10)

- Hit OK.


Also if you are looking for an SSL certificate. I got my free one from StartSSL.

- My SSL Cert included autodiscover.publicdomain.com.au and mail.publicdomain.com.au only.


I hope this helps someone.


Again, I'm not a pro at this as I'm still learning however the above method worked well for me.


Thanks for the help

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