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Emails Bouncing Back With Code 5.4.4

Hello,

A week or so ago a client of our's started getting emails bounced back when sending to yahoo.com email addresses from their exchange server. The error message they are getting is: #554 5.4.4 SMTPSEND.DNS.MxLoopback; DNS records for this domain are configured in a loop ##

Upon troubleshooting I discovered that the server was not resolving two of the three mx records for yahoo. I manually added them to the hosts file and it started working. But it turns out that the ip addresses to the which the a records point to that are being used for the mx records change periodically. So every time the IP addresses change, it breaks the fix and I have to go in and edit the hosts file again. Was wondering if anyone has any suggestions as to what might be causing this. There is no issue sending to any other email domains, including the other major email players such as aol, Hotmail, or gmail. I'm not sure what logs or other information to provide in this case, but I will put some information on the server and the setup below. Let me know what else to provide and I'll do so. Thanks.

Server OS: SBS 2011
DNS Setup: Have the DNS server forwarding external DNS queries to the ISP DNS server ip addresses

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Jamie McKillop

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ctagle

ASKER

I apologize for the late response, I thought I responded yesterday but it must have not posted it. I've done an nslookup directly against the ISP's DNS servers and compared them to the mxlookup on mxtoolbox and they are coming back correctly. The server will pull the mx records just fine, but when I try to ping the a records that it pulls from the nslookup it won't resolve the ip address. It will ping it just fine if I ping the ip address itself, but it just won't look it up on its own for some reason.

As an update, I tested it this morning after restarting the server last night to install some updates and it now will ping 2 of the three records, but it still will not ping one of them. the record is below. if I ping that same record from my computer at my office, which is using the same ISP and same DNS servers (different public ip) it will resolve and I get replies

non-pingable mx record: mta5.am0.yahoodns.net

systemcare

I am having the same issue on several of my SBS servers I support. They are on Different ISP’s and Locations. I had to put yahoodns.net ip numbers in the hosts files to get it working.
It is intermittent problem. When I do nslookup it sometimes respond 127.0.0.1 for one of yahoo’s mx record. Most of the time they are correct. I noticed the mx IP # changes constantly.

ctagle

ASKER

I set that up as well, but because it changes its not really a solution because I have to go in and modify the records all the time. but the client hasn't called in a long while and I checked and for some reason it started working all on its own, not to sure what happened. I'll go ahead and close this out, thank you all for your responses.

ctagle

ASKER

good troubleshooting tip for anyone else who is experiencing this issue. by doing an mxlookup with nslookup then you can tell if the server is able to see the mx records for the email address to which the email is trying to flow to.