Earthlink Blocking Our E-mail 1

[ebo1813]

Does anyone have any ideas on how to work around Earthlink blocking all e-mails from my mail server? Our website is hosted by a different company, on a different IP subnet. Our Exchange 2003 box is here in my office. Two totally different IP ranges. Whenever anyone from my company sends (or replies) to an username@earthlink.com message, it gets kicked back. From what I have seen, if your .com and MX records are not on the same subnet, it will reject it as SPAM.

We have customers that use the earthlink address and we cannot reply to them. VERY FRUSTRATING!

Thanks in advance!

 

[MDonato]

It wouldn't have anything to do with what subnet things are located on. It's more likely that their mail servers are performing a reverse dns lookup and can't find a correct entry for your mail server. Make sure that your mail server has a Host(A) record and MX records on both primary and secondary DNS servers for your domain.

Michael A. Dontato MCNE, MCSE, CCA
mdonato@site-technologies.com

http://www.site-technologies.com

 

[ebo1813]

Thanks for your response! I asgree with your theory. I did a little more research on the issue and noticed on

http://www.dnsstuff.com

that we in fact did not have a reverse DNS. I called my ISP and after adding it, it appears to be working great. Thanks again for taking the time to answer!

 

[GaryL]

MD is right, you need to make sure you have a PTR record.
Also,
In Exchange 2000 and 2003, look at SMTP Default virtual server, Properties, Delivery, Advanced, FQDN. Make sure what's listed there is the public FQDN of your mail server (e.g. your MX record). For example, you might have mail.mydomain.org listed in public DNS, but internally the server might be called fred.mydomain.org. By default, when Exchange is setup, it uses the AD DNS name (fred.mydomain.org).

 

[tek777]

I called MS and found this out. The problem is that EarthStink does not have their firewall set up right. They cannot accept UDP packets bigger then 512K on their firewalls.

The fix is do disable EDNS on Windows 2003 DNS Server.

Please see:

http://support.microsoft.com/?id=832223

 

[tek777]

Do not change your Exchange 2003 settings, this is not the recommeded way. I did that and started getting different errors. Active directory integrated with forwarders is the recommended setup for Exchange 2003 in your case. It is not an Exchange 2003 issue, yet a Windows 2003 DNS issue.

http://support.microsoft.com/?id=832223

 

[tek777]

The reverse lookup thing will slow down your mail server, in my opinion it is not necessary, and could be dangerous to use in some cases. I do not think it is recommended.

The reason why the problem you are having, to elaborate, is because earthlink's firewall does not accept UDP packets bigger then 512k. Well what is happening is that they have so many MX servers, when your Exchange 2003 is trying to respond with all of those MX servers in the UDP packet, the UDP packet is too big, and it bounces. EarthStink just drops your packet, and says something about a 550 which doesnt make sence at all. Why send back a 550, user unknown. Their errors are not even right.

I tried to deal with their tech support, and their excuses didn't even make sense. Earthlink, fix your firewall