Mail stuck in undeliverable and then it releases after about 3 minutes.

Hi all, nothing has changed, or perhaps I have just noticed this problem.

I will notice the queue building up to about 20 - 50 messages, and then they will dump into the undeliverable messages group.  After about 3 - 5 minutes they will release from there.

I have a Barracuda smarthost for the outbound mail set in the SMTP routing connector (not the virtual server) and again, nothing has changed.  I have the Barracuda set to inbound and it is working as I can send test emails in (they immediately arrive), and again, they eventually leave.  I performed the nslookup, set type = mx and did a '' lookup and it came back ok.  I am just wondering if this is something that I should really worry about or is there some registry setting that a service pack (which have not applied for a month now) may have set...

Also, yes I can telnet to barracuda pt 25 from the exchange server.  

Thanks in advance.

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RobinHumanConnect With a Mentor Commented:
Sounds like either a dns resolution issue or a barracuda relaying issue..
check your dns settings and check that the barracuda is relaying correctly
MightySWAuthor Commented:
Yes, I am getting DNSapi issues information only messages under the event viewer.  Essentially the event logs are very clean.  

Also, the smarthost is set for the IP address of the Barracuda and not the hostname.  

I can telnet to the hostname or the IP address of the Barracuda box without any issues.

Also, when I stop and start the SMTP server it sends everything pretty much immediately.

Thanks for the reply.
MightySWAuthor Commented:
Seems to flowing normally now.  

I added the exchange server into the exception list for the rate control on the barracuda.  I don't know why I didn't have it in there before and why it was working up to this point.  They only thing that I can imagine is that our Marketing dept. is sending a bunch of stuff out this close to the holidays and this Spam filter has not experienced this much outbound traffic.  By default the Barracuda will rate control anything over 50 messages in (I think) a minute.  I left that the same and performed step above.

Of course since the barracuda is directly in-line with mailflow I had to suspect it, I just wanted to check with the forum for due diligence.

Thanks for the response.
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