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Sending emails to hotmail and msn from Internal Outlook account

I get this error when we send outgoing emails from Outlook to hotmail or msn.  We currently have Exchange 2007

The following message to <name@hotmail.com> was undeliverable.
The reason for the problem:
5.1.0 - Unknown address error 550-'Requested action not taken: mailbox unavailable'

Any ideas?

I was able to successfully send an email to hotmail from a yahoo account but not from my Outlook account.
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nikhil61107
Asked:
nikhil61107
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1 Solution
 
Jon BrelieSystem ArchitectCommented:
I would make sure that you have an rDNS entry for your mailserver and that it identifies itself as such.
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nikhil61107Author Commented:
How do I do this?  I am not to familiar with Exchange
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Jon BrelieSystem ArchitectCommented:
Start ESM
Go to Servers -> Protocols
Select Default SMTP Virtual Server Properties
Go to Delivery tab
Click Advanced Button
Fully Qualified Domain Name - put what the outside DNS hostname is here
Restart SMTP Service.
 
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Jon BrelieSystem ArchitectCommented:
Additionally, to find out what your location has set for rdns, open http://www.whatismyip.com from your mail server.

open a command prompt (Start-Run: CMD, enter) and type the following:
nslookup www.xxx.yyy.zzz where wxyz is the numeric IP you get from the website above.

The returned value is what your mailserver should  be identifying itself as.  If you want to change this, you will need to work with your ISP as they handle rDNS entries for your IP.
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gaffieCommented:
Your domain name may be missing an SPF record in it DNS. Check it with this tool: http://www.kitterman.com/spf/validate.html
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rvctechCommented:
Another thing to check that is very popular, is that your email server gateway is using spam filtering software like SpamHaus or especially Trend Micro Enterprise Systems. Those will automatically block connections to services they consider to be "spam" magnets. They tend to block outgoing mail ports universally to Hotmail / MSN. If you can send to everyplace else, i would have your exchange administrator check this (or your virus system administrator) and have them add exceptions for the email addresses you are trying to send to. (or remove the filters altogether and see if that fixes the issue, then add the exceptions if this proves to be the problem.)

Just a thought. Good luck!

Robert Cook
Sr. Network Administrator CCVP / CCDA / CCNA
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nikhil61107Author Commented:
I checked the rdns and it was correct.  Where do I go to check the SPF.  I am not familiar with this.

Thanks,
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nikhil61107Author Commented:
Also, I forgot to add.  It is now affecting sending email to other domains as well.  Comcast.net is also being affected.  Yahoo email is still working?  Very werid and probably something simple once it is figured out.

Thanks,
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rvctechCommented:
You might want to do a lookup on email blacklists and make sure your domain is not listed. That can happen sometimes as a normal course of action, and other email servers will begin to deny you connections over the course of several weeks as they update to new blacklists.
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Jon BrelieSystem ArchitectCommented:
Are you certain that your mailserver is identifying itself as the address set in your rdns string?  You can verify this with the following from a command prompt:
telnet 'yourmailerver' 25

The ID should be right after the 220 response.
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nikhil61107Author Commented:
I checked the rDNS string and it came out correctly.  It showed itself.  The only thing we are checking is our ISP to see if they are blocking port 25.  Prelim findings is that they are, but are taking forever to unblock.  They are also noticing packet lose to our IP address.  Not sure if there are two issues going on.  I will keep everyone posted.  If anyone else has any suggestion on what else could be causing this issue, please let me know.  
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gaffieCommented:
When your ISP blocks port 25 you don't get any answer, just a time out. Are you using your ISP's mailserver a a smarthost? Check Exchange manager - Organisation config - Hub transport - Send connector - double click the connector and check the network tab. If so try using the other option "use DNS". If you already are using DNS try using a smarthost.
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nikhil61107Author Commented:
We are using a smarthost.  We have an ironport that we send all email through.  It seems that we had a virus that was on our network that was sending out spam.  We didn't notice it because the computer was only on for one day and then turned off.  I was on vacation during this time and so was the person.  When they returned today, it started back up again and we started getting blacklisted again.  Our firewall guy didn't lock down our port 25 hence the reason why spam was being sent out.  Port 25 should only be used by our IronPort and nothing else.  Opps on his part.
One thing that I am seeing is dropped packets from our swith to the firewall for our external IP address.  Is that normal.  success rate is about 99 percent.  
Is this due to this virus still and us being blocked.??

Any thoughts on this?

Thanks in advance.
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Jon BrelieSystem ArchitectCommented:
find the rogue system(s) on your network and neutralize them.  They could be overloading your firewall with delivery attempts.  What kind of firewall are you using?
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nikhil61107Author Commented:
We have a watchguard 750e.  When I set the repeat count higher than 200 and the datagram size over 500 is when i get dropped packets.  But if I down the default, it pings successfully 100%.  
This has been a pain in the side...
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nikhil61107Author Commented:
We had an infected computer that was not on the network for a week.  After the first removal of the Blacklist, we put on right after the computer was turned on again.  Our firewall consultant forgot to block port 25 for all traffic except from the Ironport which is why it took longer to figure out how this could be.  Cause was Blacklist and bad firewall config.
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