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Windows 2003 IIS mail server fails to connect to isp servers

I have a windows 2003 server running as a POP3 mail server using IIS. It had been working fine until 2 weeks ago. My setup is this. Desktop with Outlook, a server with several web sites and a server just running my mail. If i send email from my desktop I can only send to certain isp's. The email to ISP's that I can't send to are in the Queue folder on the mail server. So I know it's not my outlook on my desktop. At least I woldn't think it is. I can telnet and send email from the mail server with out a problem. Does anyone have any ideas?

Thanks
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whiwex
Asked:
whiwex
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1 Solution
 
Skyler KincaidNetwork/Systems EngineerCommented:
It sounds like a DNS issue to me. It is probably caused by DNS request for certain domains failing so it doesn't know where to send the mail. What are the DNS servers on your email server?

If you check the event logs do you see any errors? If you try pinging the websites for those companies do you get replies? (They may have ICMP disabled so it may or may not work anyway). When is the last time you restarted the email server or your DNS server?
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whiwexAuthor Commented:
I can ping the sites that don't work. The mail server was also configured as a DNS server.
I removed the DNS from the mail server and I still have the same problem. The mail server has been restarted several times.
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Iradat SiddiquiCommented:
Please check whether you have proper smtp connectivity

http://mxtoolbox.com/diagnostic.aspx

Do check whether your mail server is blacklisted?

http://mxtoolbox.com/blacklists.aspx
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whiwexAuthor Commented:
I found that I was blacked listed at SORBS even though it never showed up when I checked blacklists on the net.
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