Back Pressure Problem in ASP.NET Emailing
I got an error message about "Back Pressure" when I was developing a ASP.NET emailing function recently. The code and configuration are good and I have no idea what is this issue, so I search MSDN and found this page about what is "Back Pressure" (for Exchange 2010 by the way).
Finally, I found that the problem is due to insufficient space on the Exchange server. So adding/mounting new drive to that server and solve this problem immediately! I'd suggest to read that MSDN page and try this solution whenever you see error about Back Pressure of Exchange.