5.1.2

Question

I'm having an issue where people trying to send emails to me are getting bounced back randomly, sometimes they will get through but often they won't and they get these responses:
Diagnostic information for administrators:
Generating server: canat0472.ca.deloitte.com
[email protected]
#< #5.0.0 smtp; 5.1.2 - Bad destination host 'Multiple DNS queries were attempted and failed: DNS Hard Error looking up remote.tophathomecomfort.com (A): NXDomain'
(delivery attempts: 0)> #SMTP#
or
Final-Recipient: rfc822;[email protected]
Action: failed
Status: 5.7.1
Diagnostic-Code: smtp;550 5.7.1 Message rejected as spam by Content Filtering.
or
  ----- The following addresses had permanent fatal errors -----
<[email protected]>
   ----- Transcript of session follows -----
550 5.1.2 <[email protected]>... Host unknown (Name server:
remote.tophathomecomfort.com.: host not found)
I've run mx toolbox diagnostics, microsoft remote connectivity analyzer, exchange best practice analyzer and none of them have show errors other than a PTR record mismatch which shouldn't be affecting email coming through.
The frustrating thing is I'm getting a lot of email, I'm even getting email from these people occasionally, it's just happening enough that its a problem and it's not something I can personally replicate in order to test solutions.
SBS 2011 standard/exchange 2010 sp2
Godaddy for domain management
Host
Points To
TTL
69.156.241.50
600 seconds
remote
76.65.233.160
1/2 Hour
AAAA (IPv6 Host) 
Host
Points To
TTL
CName (Alias) 
Host
Points To
TTL
calendar
login.secureserver.net
1 Hour
email
email.secureserver.net
1 Hour
fax
login.secureserver.net
1 Hour
files
login.secureserver.net
1 Hour
ftp
1 Hour
imap
imap.secureserver.net
1 Hour
mail
pop.secureserver.net
1 Hour
mobilemail
mobilemail-v01.prod.mesa1.secureserver.net
1 Hour
pop
pop.secureserver.net
1 Hour
smtp
smtp.secureserver.net
1 Hour
www
1 Hour
MX (Mail Exchanger) 
Priority
Host
Points To
TTL
10
remote.tophathomecomfort.com
1/2 Hour
TXT (Text) 
Host
TXT Value
TTL
v=spf1 a mx ~all
1/2 Hour
SRV (Service) 
Service
Protocol
Name
Priority
Weight
Port
Target
TTL
_autodiscover
_tcp
0
0
443
remote.tophathomecomfort.com
1/2 Hour
NS (Nameserver) 
Host
Points To
TTL
ns1.bellhosting.com
1 Hour
ns2.bellhosting.com
1 Hour
@ (Informational)
ns51.domaincontrol.com (Informational)
1 Hour (Informational)
@ (Informational)
ns52.domaincontrol.com (Informational)
1 Hour (Informational)

Answer 1

Hi Sean,
Is it failing for all the domains mentioned or just one domain?
If it is one domain, try to find the mx record of the domain.  
If its having a problem with all the domain, it should your dns server causing this issue.
According to the error message, "Diagnostic-Code: smtp;550 5.7.1 Message rejected as spam by Content Filtering."
For this issue, please follow these steps to perform troubleshooting:
1. Please check whether we are using transport agent via following command:
Get-TransportAgent
Link for your reference: http://technet.microsoft.com/en-us/library/bb123536(v=exchg.141).aspx
If have, please disable them for testing.
2. Please make sure we are not using any third party tool on Exchange Server, disable them for testing.
Hope it is helpful
Thanks
Mavis
Mavis Huang
TechNet Community Support