When the mail is not received by the mail server and you receive the error message from your mail gateway or a telnet client:
said: 452 4.3.1 Insufficient system resources (in reply to MAIL FROM command)
Or there is a event id 15006:
Microsoft Exchange Transport is rejecting message submissions because the available disk space has dropped below the configured threshold.
The following resources are under pressure:
Queue database logging disk space (“D:\Programs\Microsoft Exchange 2010\TransportRoles\data\Queue\”) = 60% [Medium] [Normal=58% Medium=60% High=62%]
Then the problem is that there are to less system recourses. In this case the disk space where the queue is, is to small. You can resize the volume or you can change the queue location in the file:
Exchange installation Directory\Bin\EdgeTransport.exe.config
You must change the following to keys:
<add key=”QueueDatabasePath” value = “D:\Queue”/>
<add key=”QueueDatabaseLoggingPath” value = “D:\QueueLog”/>
After this you must restart the Exchange Transport Service.