Hello, Can someone point me in the right direction to start debugging this problem? I am an advanced power user and developer but a beginning networks admin (mine is on holiday at the moment). We are using Exchange 2007. Many thanks. Keith

Well first of: did it work before? If so, did something change in the meanwhile? are there any error messages (perhaps an NDR that someone is getting when trying to mail you?) There are numerous things that might prevent mail from flowing in, so in order to help you would need to give us a bit more information. Michael

Hi You can start with using www.mxtoolbox.com and do a SMTP test Check with the firewall crew that everything looks ok, try to trance the smtp traffic (port 25). Check rules and port forwarding/nat etc. Do you have any update on your issue?Jonas Andersson | Microsoft Community Contributor Award 2011 | MCITP: EMA 2007/2010 | Blog: http://www.testlabs.se/blog | Follow me on twitter: jonand82

Michael, Thanks for the initial comment. I sent an email to my work account from my GMail account, the email bounced back, and the following showed up in my GMail account. Delivery to the following recipient has been delayed: [My work email address] Message will be retried for 2 more day(s) Technical details of temporary failure: Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 452 452 4.3.1 Insufficient system resources (state 13). I looke up the above codes on the internet and it seems that the problem may be related to system resources and Back Pressure. I read various articles about how to change Back Pressure settings, but I understand that that is quite dangerous, and, instead, I should locate the source of the problem. It seems likely (to me at least!) that I need to free up resources. I don't know where to start looking and what to delete. How can I find out what to delete? Also, for your reference, we were receiving emails fine up until 28 Feb at around 9am (i.e. around 2 days ago). Many thanks. Keith

Hello all, (With some key help from my networks admin, who I was able to locate and talk to offsite), I found and fixed the problem. Basically, a daily Exchange log was being saved in C:\Windows\System32\winevt\Logs. After several months of daily saves, the C: drive had only around 2 Gigs of space left, and Exchange seemed to stop delivering incoming emails. I deleted a couple of hundred old logs from this location, so that I now have 25 Gigs left on C:\ of the server. A (excruciatingly slow) back-log of emails started to dribble in almost immediately. This has continued for the past several hours. I guess the source computers on the internet that originally tried to send emails to our server do a "send re-try" at differing frequencies, so I guess it could be a couple of days until the back-log is cleared. Many thanks for your help. Kind regards, Keith