Remote Server returned '400 4.4.7 Message delayed'

Question

I have been getting the "error" in the subject lately.  It only happens on some emails and generally to only some recipient domains (gmail being one) but not even all the time for them.  The emails do always get delivered but are delayed
for several hours at least each time.  It's becoming an issue as it is fairly often now, and I would like to find a solution.  Since it's happening to recipients other than just gmail, and as far as I can tell sending from my domain is the only one
having this issue, there must be something wrong internally.
Delayed bounce message:
Diagnostic information for administrators:
Generating server: MyMachine.MyDomain.local
[email protected] Remote Server returned '400 4.4.7 Message delayed'
Original message headers:
Received: from
MyMachine.MyDomain.local (192.168.1.3) by  MyMachine.MyDomain.local
(192.168.1.3) with Microsoft SMTP Server (TLS) id  15.0.712.24; Tue, 3 Dec 2013 12:34:48 -0500 Received: from
MyMachine.MyDomain.local ([::1]) by
MyMachine.MyDomain.local  ([::1]) with mapi id 15.00.0712.012; Tue,
3 Dec 2013 12:34:36 -0500 From: Me <[email protected]> To: " Somebody  <[email protected]> Subject: start Thread-Topic: start
Thread-Index: Ac7wTe7MQ15PInWfSkyzZYwfpa+47Q== Date: Tue, 3 Dec 2013 17:34:35 +0000 Message-ID: <[email protected]>
Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: x-originating-ip: [192.168.1.52] Content-Type: multipart/related;             boundary="_004_f67e412e61524289af789970d3a3ff22MyMachineMyDomainlocal_";
            type="multipart/alternative" MIME-Version: 1.0
When the message is in the Exchange Queue, it says:
"451 4.4.0 DNS query failed. The error was: DNS query failed with error ErrorTimeout"
I ran SMTPDiag and everything passed.  I can copy/paste the results if needed.
Other info that may be helpful:
Email server domain:  mail.MyExternalDomain.com
Mail is SENT from:  IPaddress1
Mail is accessed remotely (OWA/outlook/active sync) via:  IPaddress2          (2 ip addresses here to easily route through firewall)
The mx record points to our spam filter's domain name, our offsite spam protection, so that naturally doesn’t match ours.
The Exchange send connector is set to have a FQDN of mail.MyExternalDomain.com for responses to HELO/EHLO
I had our ISP set IPaddress1 to have an rdns of mail.MyExternalDomain.com
I'm unsure that the recipient's server is the one even delaying it so the DNS info may not be a factor.  It seems to me to be something internal but I can't figure out what that may be.
Thank you for any suggestions!

Answer 1

Hi IMGooch,
Which kind of IP do we have, a static public IP or a dynamic one? 
Are we on a residential Internet connection or Business? 
I ask that because if we are using dynamic IP or a residential connection, the ISP might be blocking port 25. 
Please try to do a test telnet outwards. 
We can also use the ISP's smtp server through Smart Hosts.
Hope it is helpful
Thanks
Mavis
Mavis Huang
TechNet Community Support