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451 5.7.3 Cannot achieve Exchange Server authentication Error Exchange 2007

Hi everyone,
Im in the middle of an Exchange 2003 to Exchange 2007 transition, and i have come to an issue. Ill explain our mail setup, we have one exchange 2003 server which also hosts our spam filters (not a good setup but works for now). The spam filters on that machine has the smtp port set to 25 and i had to set the smtp port on exchange to 26, now with the exchange 2007 server added i cant send internal mail to the old exchange server it just sits in the que with this error "451 5.7.3 Cannot achieve Exchange Server authentication" now i have done some reading and found out that this probably due the the non standard smtp port that exchange 2003 is running on, as i have checked securities and authentication. Now what im asking is how do i tell exchange 2007 to send mail to port 26 on the old exchange server?

Justin Durrant

Is Integrated Windows Authentication turned on the Default SMTP Virtual Server?

zeroburnfire

ASKER

Yes it is, that was one of the first things i checked! On both exchange servers IWA is turned on.

Justin Durrant

I am not sure the port can be changed.. have you tried switching from 26 to 25 just to be sure that is the issue?

zeroburnfire

ASKER

Ok just tried that, and with out any luck same issue! Hmm... i guess im totally out of ideas on why im getting this error message then!

Justin Durrant

Hmm.. worked for this guy https://www.experts-exchange.com/questions/22638022/451-5-7-3-Cannot-achieve-Exchange-Server-authentication-between-Excahnge-2007-and-2003.html

Justin Durrant

Are you using TLS?

zeroburnfire

ASKER

Yea i had looked at that post and realized maybe that was an issue with being on port 26 thats why i asked my question.

On both servers TLS is not checked off for security. Should i check them off and give it a try?

zeroburnfire

ASKER

One thing that i know for a fact and this might help out. Today i added a new send connector to send mail out to the net as it was just queuing the emails. When i did that, thats when internal emails stoped going through to the other exchange server. I referred to MS KB556055 to do that.

Justin Durrant

Look over: http://www.msexchange.org/tutorials/Transitioning-Exchange-2000-2003-Exchange-Server-2007-Part1.html

zeroburnfire

ASKER

Yea that was the guide that i followed when doing my prep and install of exchange 2007.

zeroburnfire

ASKER

Anybody else have any ideas?

zeroburnfire

ASKER

ok found this in my log files and the only thing i see wrong is under cn=uhca probbly should read cn=uhca1 as thats the domain. Am i correct in thinking that?

2008-10-16T00:09:10.514Z,08CAFC3BFD8D6359,SMTP,"cn=first routing group,cn=routing groups,cn=first administrative group,cn=administrative groups,cn=uhca,cn=microsoft exchange,cn=services,cn=configuration,dc=uhca1,dc=local",+,e237e528-e744-429b-8f6a-6e34a0344161
2008-10-16T00:09:10.514Z,08CAFC3BFD8D6359,SMTP,"cn=first routing group,cn=routing groups,cn=first administrative group,cn=administrative groups,cn=uhca,cn=microsoft exchange,cn=services,cn=configuration,dc=uhca1,dc=local",>,"mail.uhca1.local[10.10.0.6, 10.10.0.75]"
2008-10-16T00:09:10.514Z,08CAFC3BFD8D6359,SMTP,"cn=first routing group,cn=routing groups,cn=first administrative group,cn=administrative groups,cn=uhca,cn=microsoft exchange,cn=services,cn=configuration,dc=uhca1,dc=local",>,Established connection to 10.10.0.6
2008-10-16T00:09:11.092Z,08CAFC3BFD8D6359,SMTP,"cn=first routing group,cn=routing groups,cn=first administrative group,cn=administrative groups,cn=uhca,cn=microsoft exchange,cn=services,cn=configuration,dc=uhca1,dc=local",>,Established connection to 10.10.0.75
2008-10-16T00:09:12.827Z,08CAFC3BFD8D6359,SMTP,"cn=first routing group,cn=routing groups,cn=first administrative group,cn=administrative groups,cn=uhca,cn=microsoft exchange,cn=services,cn=configuration,dc=uhca1,dc=local",-,Retry

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zeroburnfire

ASKER

The port is set to 26. This is because we have a email filter set up on the same server that accepts all the mail on port 25 and sends it to the exchange server on port 26.

Exchange_Geek

Great, in that case please use telnet from E2k7 box to drop and email on E2k3 to check if the mail flow works fine over RGC.

zeroburnfire

ASKER

Ok issues solved! This came back to my orginal question about the ports. Yesterday our email filter decided to crap out and support sucks on it so i turned it off and set my smtp port on exchange 03 back to 25. Once i did that my error went away and mail is flowing great between my 2 exchange servers! So if you use any port other than 25 when doing a transition from exchange 2003 to exchange 2007 make sure exchange 2003 is on 25! Since im new here and i solved my own question i have no idea on points, but im willing to give them out to all that helped me.