We are running a SBS 2008 server with exchange 2007.Every now and then we can't receive incoming external e-mail.Sending e-mail and receiving internal e-mail works fine.After restarting the SMTP service everything works fine again.When the problem occurs, telnet to port 25 doesn't work anymore.Several tests proved this is nog a firewall problem. Does anyone have a idea what is causing this problem? Regards, Wim Tomassen

Hi wim,Is it a very specific time that this happens?What kind of FW are you using? Also can you tell us the flow of icoming emails??Raj

Hai Raj,Thanks for you reply.The last two times the problem happened around 15:00 hr on Wednesday.Previously it happened also on other days. It's also not every week.Sometimes it's running fine for almost 3 weeks.All external mail is redirected by the DNS MX record to the Draytek 2700 router.Port 25 is redirected to the SBS server.We are using a Draytek2700 router with some FW functionality.We are usingAVG Anti-Virus SBS Edition.All OWA functionality also works fine. It's only incoming external mail.Below the MX DNS configuration. IP adres MX Prio Descriptionmail.awe-tech.nl 89.184.191.43 10 (Draytek 2700 router)mailbackup.mysmt.net 20 (Mail backup server hosting company)I saw exactly the some problem at Exchange Server TechCenter > Exchange Server Forums > Transport > SMTP incoming mail delivery stops (Exchange Server 2007) The solution however is not publiced (yet).Thanks for the support. Wim

Just check , if the the router is holding upto the config. Also , as you said when the mail stops, even the telnet stops on 25. For sure this is either a network or the FW issue.Raj

When you telnet on port 25 is it directly to the server on your LAN? Or are you trying to route from the internet?Based on past experience I would suspect your AV or something with your NIC.SF - MCITP:EMA, MCTS: MOSS 2007, OCS 2007, Exchange 2007 -- http://www.scottfeltmann.com

Hello,I would check that Draytel 2700. I just tried to telnet to mail.awe-tech.nl and there is no response. The server backup.mysmt.net does respons with 220.1. Check that there is not firewall rule that denies inboundSMTP based on a schedule2. If you do not find a patter to port 25 being blocked, update Draytel firmware, reset firmware, try new router,etc; there may be a bug or a config error of some sort and you maybe experiencing anintermittent problem. 3. And as mentioned by Scott, certain AV programs block SMTPtrafficif AV isnot up-to-date. Check that as well.When the problem occurs try this and let us know the response:from server telnet 127.0.0.1 25from workstation telnet serverip 25from outside telnet fqdn 25from outside telnet ipaddress 25Miguel Fra / Falcon ITS Miguel Fra / Falcon ITS Computer and Network Services, Miami, FL http://www.falconits.com

Please also check when the problem occurs that your SMTP service is running....Miguel Fra / Falcon ITS Computer and Network Services, Miami, FL http://www.falconits.com

Scott, Miguel, Raj, Thank you all for the support and suggestions. I will continue with testing as soon as the problem occurs again.Regards,Wim TomassenThe Netherlands

Hi,When the problem occur again,please also check event log.There we could have related event logged.Also you can configure protocol logging on exchange server.Related information to share withyou: How to Configure Protocol Logging http://technet.microsoft.com/en-us/library/bb124531.aspxRegards,Xiu