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Exchange email does not make it to destination

We are managing an exchange server for a client and they are experiencing problems sending to only one domain.

The domain is hk.starcont.com

The client can send from private POP accounts such as gmail. We can send from our Exchange email accounts. Our Exchange and our clients use separate servers.

Most times when our client sends email to this domain, they do not get a bounce back email.

Our Exchange engineers have confirmed that the emails are leaving our clients exchange server.

Using MXToolbox's DNS lookup tool:

No Results Found

smtp diag


port scan

http test

Reported by zimdns.hk.starcont.com on Wednesday, January 16, 2013 at 2:15:24 AM (UTC -6)  Transcript

We have asked starcont.com to make sure that this client's emails are not being filtered / blocked by proofpoint or other firewalls. and they have responded back that there is nothing blocking them.

Any help or suggestions is appreciated.
4 Solutions
Neil RussellTechnical Development LeadCommented:
"Most times when our client sends email to this domain, they do not get a bounce back email"

Does this mean you sometimes do? If so can we have the details please?
You used mxtoolbox (would start from it, too): the Exchange server's IP isn't listed in any Blacklist, right?
The mail leaves the Exchange server: to which destination IP or FQDN?
Destination server's engineers confirmed there's nothing blocking. Do they find any sign of the mail arriving from your server?
Andrew DavisManagerCommented:

MX lookup for hk.starcont.com reveals
100 mxcon.hk.starcont.com.
50 mailbackup.hk.starcont.com.
20 hfzbmgmt.zim.com.
20 hfzbm1.zim.com.
20 hfzbm2.zim.com.
10 mail.hk.starcont.com.
10 mail1.hk.starcont.com.

Thats 7 mx records. thats a lot. (Even Gmail only has 5)

by telneting to each in turn they all respond with different names than their FQDN.
mxcon doesnt respond at all.

you need to track where your email are trying to go to.
How do your email travel to them? does your exchange do the DNS or are you smart hosting through an external source?

The reciever needs to really fix their MX records. But if you are sending via DNS then you could find one of their MX records that does work and then create your own DNS zone for them and set the preferred, But that is a really ugly way of doing it.

Hi there.

Are you using the Windows resolver or the Exchange "external DNS" resolver. If it is windows then make sure your DNS server has the root hints configured, if so, the email can be sent directly to its internet destination domain..MX records for that domain are as follows:

hk.starcont.com MX (Mail Exchanger) Priority: 100 mxcon.hk.starcont.com
hk.starcont.com MX (Mail Exchanger) Priority: 50 mailbackup.hk.starcont.com
hk.starcont.com MX (Mail Exchanger) Priority: 20 hfzbmgmt.zim.com
hk.starcont.com MX (Mail Exchanger) Priority: 20 hfzbm1.zim.com
hk.starcont.com MX (Mail Exchanger) Priority: 20 hfzbm2.zim.com
hk.starcont.com MX (Mail Exchanger) Priority: 10 mail.hk.starcont.com
hk.starcont.com MX (Mail Exchanger) Priority: 10 mail1.hk.starcont.com
mxcon.hk.starcont.com A (Address)

Check with your ISP if you resolve with them.
Hope this fixes your issue.
RSchiererAuthor Commented:
Thanks guys you have given me a lot of good info and direction where I should concentrate my efforts.
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