issues with email being rejected on exchange

junaidIT used Ask the Experts™
Greetings Experts,

Need urgent help. Got issue with email being rejected. getting reason given below on my barracuda.

451 Internal resource temporarily unavailable.
501 5.1.7 Bad sender address syntax( barracuda shows as the ip being in greylist)

I am trying to do telnet the recepient mail server and still get the same message. Please advice if this is a trouble on our side or the recepient and how can this be fixed.

Also have issues with email delivery being delayed. Could this be anything to do with the DNS. my firewall only has one DNS entry in it. should i add the remaining dns servers also for our ISP?

Also is it recommended to add the google dns to the infrastructure DC for forwarders and also on the firewall.

All trouble recently started. The environment has been stable and havent had issues so far. so a bit panicky.

My exchange is 2007 sp2 with two nodes on ccr and two hub transport servers which forward the email to barracuda. Outgoing everything is allowed from trust to untrust on my juniper firewall.
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junaidITManager, ICT Services


the problem is with the oubound emails only. When i ran an smtp diag from a third party website, i got these results :

       Warning - Reverse DNS does not match SMTP Banner
 Warning - Does not support TLS.
 0 seconds - Goodon Connection time
 OK - Not an open relay.
 7.301 seconds - Warning on Transaction Time

how can this be sorted out.

sorry if asking everything in one question.
Rodney BarnhardtServer Administrator

First, use to run some test on your mail IP address.

There are also other options to test to make sure you are not on some spam list as well. has some tools that may be able to help
junaidITManager, ICT Services


i have used mxtoolbox to diagnoze and didnt see any errors. have a new issue that has popped up. A email send to a particular domain gets deferred.

The weird thing is , if i send a email with no attachment nor much message body content , it is working.

barracuda guys were on thel ine, they did a packet capture and are saying, the smtp connection from receiving end could be getting closed before their email scanner finishes the scanning. also the log shows that my barracuda is trying to resend the message.

any ideas about what to do . i am stuck with this issue.

thanks in advance,
Server Administrator
Typically what I do on a problem like this is try to get in touch with the admin on the receiving end. We have customers, partners, etc where we have such problems every week. Either we get bounced or they are getting bounced. I usually try to get a contact and work with the admin on the other end. That always gets it resolved.
junaidITManager, ICT Services


problem turned out to be with recipient. thanks again.

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